U.S. patent application number 16/794963 was filed with the patent office on 2020-06-11 for dressing system.
The applicant listed for this patent is Edixomed Limited First Water Limited. Invention is credited to Nicholas Boote, Hugh Munro.
Application Number | 20200179558 16/794963 |
Document ID | / |
Family ID | 55177361 |
Filed Date | 2020-06-11 |
United States Patent
Application |
20200179558 |
Kind Code |
A1 |
Munro; Hugh ; et
al. |
June 11, 2020 |
Dressing System
Abstract
The present invention relates to skin dressings that are useful
in the treatment of conditions associated with tissue ischaemia and
skin lesions including those that are infected, such as burns and
surgical wounds and chronic wounds such as but not limited5 to
diabetic foot ulcers and venous leg ulcers. The skin dressings are
also useful to effect transdermal delivery of pharmaceutically
active agents.
Inventors: |
Munro; Hugh; (Edinburgh
Midlothian, GB) ; Boote; Nicholas; (Marlborough,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Edixomed Limited
First Water Limited |
Edinburgh Midlothian
Marlborough |
|
GB
GB |
|
|
Family ID: |
55177361 |
Appl. No.: |
16/794963 |
Filed: |
February 19, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15779147 |
May 25, 2018 |
10603401 |
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PCT/GB2016/053727 |
Nov 28, 2016 |
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16794963 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61K 31/445 20130101;
A61L 15/44 20130101; A61K 33/00 20130101; A61K 31/245 20130101;
A61K 31/46 20130101; A61L 26/0066 20130101; A61L 15/28 20130101;
A61L 2300/114 20130101; A61K 9/7007 20130101; A61K 31/167 20130101;
A61L 15/24 20130101; A61L 2300/402 20130101 |
International
Class: |
A61L 15/44 20060101
A61L015/44; A61K 9/70 20060101 A61K009/70; A61K 31/167 20060101
A61K031/167; A61L 26/00 20060101 A61L026/00; A61K 31/445 20060101
A61K031/445; A61K 31/46 20060101 A61K031/46; A61K 31/245 20060101
A61K031/245; A61K 33/00 20060101 A61K033/00; A61L 15/24 20060101
A61L015/24; A61L 15/28 20060101 A61L015/28 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2015 |
GB |
1520990.1 |
Claims
1-36. (canceled)
37. A system comprising: a layer containing a nitrite; and a layer
comprising a source of hydrogen ions, wherein the layer is not a
hydrogel.
38. The system according to claim 37, wherein the layer comprising
the source of hydrogen ions is a carboxymethylcellulose, an
alginate, or a gelling fibre, or a mixture thereof.
39. The system according to claim 37, wherein the layer comprising
the source of hydrogen ions is a superabsorbent dressing based on
sodium polyacrylate.
40. The system according to claim 37, wherein the layer comprising
the source of hydrogen ions is a honey-based dressing.
41. The system according to claim 37, wherein the layer containing
the nitrite is a mesh.
42. The system according to claim 41, wherein the mesh is formed of
a polymer.
43. The system according to claim 42, wherein the polymer is
polypropylene.
44. The system according to claim 37, wherein the layer containing
the nitrite is a dissolvable film.
45. The system according to claim 44, wherein the dissolvable film
is formed of a polyvinyl alcohol, polyvinylpyrrolidone, a
cellulose-based polymer, or cellulose.
46. The system according to claim 37, wherein the nitrite is an
alkaline metal nitrite or an alkaline earth metal nitrite.
47. The system according to claim 46, wherein the nitrite is sodium
nitrite.
48. The system according to claim 37, wherein the system comprises
a plurality of layers containing a nitrite.
49. The system according to claim 37, wherein the nitrite is
present as a nitrite solution.
50. The system according to claim 37, wherein the pH of the layer
comprising the source of hydrogen ions is below 5.5.
51. The system according to claim 37, wherein the system does not
contain a thiol or a reductant.
52. The system according to claim 37, further comprising a
pharmaceutically active agent.
53. A method of treating a subject having a condition associated
with tissue ischaemia or a wound, comprising administering the
system according to claim 37 to the subject in need thereof.
54. A kit comprising: a layer containing a nitrite; and a layer
comprising a source of hydrogen ions, wherein the layer is not a
hydrogel, as a combined preparation suitable for simultaneous,
separate, or sequential use in treating a condition associated with
tissue ischaemia or a wound.
55. A method of treating a subject having a disease or medical
condition, comprising administering the system according to claim
52 to the subject in need thereof.
56. A kit comprising: a layer containing a nitrite; and a layer
comprising a source of hydrogen ions, wherein the layer is not a
hydrogel, as a combined preparation suitable for simultaneous,
separate, or sequential use in treating a disease or condition,
wherein the layer containing the nitrite and/or the layer
comprising the source of hydrogen ions comprises a pharmaceutically
active agent.
57. The system according to claim 37, comprising: a layer
containing a nitrite; and a layer comprising a source of hydrogen
ions, wherein the layer is not a hydrogel, in combination with an
anaesthetic suitable for use in the treatment or prevention of
pain.
58. The system according to claim 57, wherein the system is
designed for simultaneous, separate, or sequential administration
with the anaesthetic.
59. The system according to claim 58, wherein the anaesthetic is
selected from the group consisting of lignocaine (lidocaine),
amethocaine (tetracaine), xylocaine, bupivacaine, prilocaine,
ropivacaine, benzocaine, mepivocaine, and cocaine, or a mixture
thereof.
60. A method of treating a condition associated with tissue
ischaemia or a wound in a subject in need thereof, comprising
administering to the subject an anaesthetic and a system according
to claim 37.
61. The method according to claim 60, wherein the wound is an
ulcer.
62. The method according to claim 61, wherein the ulcer is a leg
ulcer, pressure ulcer, or diabetic ulcer.
63. The method according to claim 60, wherein the wound is a skin
donor site, a surgical wound, a burn, a laceration, or an
abrasion.
64. The method according to claim 60, wherein the condition
associated with tissue ischaemia is Raynaud's syndrome, or tissue
ischaemia caused by septic shock, irradiation, or a peripheral
vascular disease.
65. A system comprising: a layer containing a nitrite; and a layer
comprising a source of hydrogen ions, wherein the layer is: a
gelling fibre, an alginate, or carboxymethylcellulose, or a mixture
thereof; a superabsorbent dressing based on sodium polyacrylate; or
a honey-based dressing.
66. The system according to claim 65, wherein the layer comprising
the source of hydrogen ions is not a hydrogel.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to skin dressings that are
useful in the treatment of conditions associated with tissue
ischaemia and skin lesions including those that are infected, such
as burns and surgical wounds and chronic wounds such as but not
limited to diabetic foot ulcers and venous leg ulcers. The skin
dressings are also useful to effect transdermal delivery of
pharmaceutically active agents.
BACKGROUND TO THE INVENTION
[0002] Nitric oxide (NO) is a potent vasodilator, synthesised and
released by vascular endothelial cells and plays an important role
in regulating local vascular resistance and blood flow.
Biologically, nitric oxide (NO) is generated from L-arginine via NO
synthase enzymes and performs a variety of functions, including
vasodilatation and host defence. NO is also manufactured on
epithelial surfaces (such as in the mouth and stomach, and on the
skin surface) in humans by sequential reduction of nitrate and
nitrite. This relies on the synthesis of nitrite by the bacterial
reduction of inorganic nitrate present in saliva, mucosal
secretions or sweat. Nitrite is further reduced to NO in an acidic
environment.
[0003] The combination of acid and nitrite is effective in killing
a wide variety of pathogens by the generation of NO and oxides of
nitrogen such as nitrogen dioxide (NO.sub.2). It is likely that NO
generated in this way has a significant role in host defence
against microbial pathogens, many of which are known to be
susceptible to this agent.
[0004] A system has previously been devised that mimics this
endogenous mechanism of NO generation, using inorganic nitrite and
an organic acid to produce NO on the skin surface. This method
relies on keeping the components separate until applied directly to
the skin. Individually, these components elicit no significant
effects.
[0005] WO 2000/053193 relates to the use of acidified nitrite as an
agent to cause local production of nitric oxide at the skin surface
for the treatment of peripheral ischaemia and associated conditions
such as Raynaud's phenomenon and wounds such as post-operative
wounds and burns. In some embodiments, a barrier consisting of a
membrane allows diffusion of the nitrite ions while preventing
direct contact of the acidifying agent with the skin.
[0006] It has also previously been discovered that a system using
inorganic nitrite and an organic acid to produce NO on the skin
surface can be used for the transdermal delivery of
pharmaceutically active agents.
[0007] WO 02/17881 discloses a transdermal delivery system
comprising a pharmaceutically active agent and acidified nitrite as
an agent to cause local production of nitric oxide at the skin
surface. Also disclosed is the use of a barrier consisting of a
membrane to allow diffusion of the pharmaceutically active agent
and nitrite ions while preventing direct contact of the acidifying
agent with the skin.
[0008] WO/2014/188174 and WO/2014/188175 describe systems
comprising a layer containing a nitrite and a hydrogel that
contains hydrogen ions. These disclosures originate from one or
more of the members of the inventive entity of the present
application.
SUMMARY OF THE INVENTION
[0009] The present inventors have developed an improved dressing
system that is useful in the treatment of conditions associated
with tissue ischaemia and skin lesions, including those that are
infected, such as burns and surgical wounds and chronic wounds such
as but not limited to diabetic foot ulcers and venous leg ulcers,
and can also be used as a transdermal delivery system. The dressing
makes use of a first layer containing a nitrite and a second layer
containing a source of hydrogen ions to provide the acidifying
effect on a nitrite for the production of NO. The inventors have
surprisingly found that the heterogeneous reaction system created
by these separate layers in such a dressing system is advantageous
since it results in a reduced amount of the NO.sub.2 by-product of
the reaction to produce NO, whilst producing NO at therapeutic
levels.
[0010] Accordingly, in a first embodiment the present invention
provides a system comprising: [0011] (i) a layer containing a
nitrite; and [0012] (ii) a layer comprising a source of hydrogen
ions.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The system of the invention is a dressing system. A
"dressing", as will be well known to a person of skill in the art,
is something that is applied to the skin of a human or animal to
cover, protect and/or treat a lesion on the skin of the human or
animal. A dressing is suitable for use in relation to any breakage
or interruption in the skin barrier, which can be caused, for
example, by ulcers, surgery, burns, cuts, lacerations, trauma
and/or abrasions.
[0014] The system of the invention is a two component system,
comprising a first component which comprises a layer containing a
nitrite and a second component comprising a source of hydrogen
ions. The layer comprising a source of hydrogen (H.sup.+) ions has
an acidic pH. The two components can in fact be considered as two
separate dressings. When the two components are placed in contact
with each other, a chemical reaction takes place to produce nitric
oxide (NO). The two components will now be described in detail.
[0015] The first component of the system of the invention comprises
or is a layer containing a nitrite. The layer is permeable (fully
permeable or at least semi-permeable) to the diffusion of nitric
oxide, which forms when the first and second components of the
dressing are placed in contact with each other. The first component
of the system of the invention is typically placed in direct
contact with the skin (i.e. on a wound or ulcer) during use, and
should not adhere to the skin and/or cause damage to the wound bed
or friable wound tissue. The layer can therefore be described as a
wound contact layer. The layer can therefore be made of any
material that is suitable for this purpose and which can be
impregnated with, imbibed with or otherwise contain a nitrite. The
layer is typically, but not limited to, a mesh, non-woven bat,
film, foam, alginate, amorphous hydrogel, crosslinked hydrogel or a
membrane.
[0016] In one embodiment, the layer is a mesh. A mesh consists of
connected strands of solid, typically flexible material, that form
a lattice with holes or gaps through which certain substances can
pass. The mesh can be woven or non-woven, but is typically
non-woven.
[0017] The mesh is typically made of a polymeric material. Any
polymeric material is suitable, for example viscose, polyamide,
polyester, polypropylene or blends of these, but a preferred
polymeric material is polypropylene.
[0018] In another embodiment, the layer is a dissolvable film. The
term "dissolvable film" includes polymers with solubility in water.
Examples include polyvinyl alcohols or polyvinylpyrrolidones and
cellulose-based polymers for example hydroxypropylcellulose or
carboxymethylcellulose.
[0019] Such a film can be made of any suitable material, for
example cellulose.
[0020] In some embodiments, the system of the invention comprises a
plurality of (i.e. more than one) layers containing a nitrite. For
example, the system of the invention can comprise 2, 3, 4, 5, 6, 7,
8, 9 or 10 or more layers containing a nitrite. For example, the
system of the invention can comprise a plurality of meshes imbibed
with a nitrite, for example as a nitrite solution. Typically, when
a plurality of layers is used, each of the layers is formed of the
same material, for example a mesh or a dissolvable film.
[0021] In one embodiment, the layer is not a membrane and/or a gel,
for example a hydrogel.
[0022] The layer contains a nitrite salt in solid or solution form.
Typically, the nitrite is in the form of a nitrite solution. The
layer is typically imbibed or impregnated with the nitrite, for
example by soaking the layer in a solution of the nitrite. The
nitrite is typically a pharmacologically acceptable source of
nitrite ions or a nitrite precursor thereof.
[0023] The layer (such as a mesh) functions to retain the nitrite
solution essentially within a region defined by the area of the
layer (such as a mesh). This provides for ease of application of
the dressing to the skin and/or wound.
[0024] The pharmacologically acceptable source of nitrite ions may
be an alkaline metal nitrite or an alkaline earth metal nitrite.
For example, LiNO.sub.2, NaNO.sub.2, KNO.sub.2, RbNO.sub.2,
CsNO.sub.2, FrNO.sub.2, Be(NO.sub.2).sub.2, Mg(NO.sub.2).sub.2,
Ca(NO.sub.2).sub.2, Sr(NO.sub.2).sub.2, Ba(NO.sub.2).sub.2, or
Ra(NO.sub.2).sub.2. In a preferred embodiment the nitrite is sodium
nitrite (NaNO.sub.2), potassium nitrite (KNO.sub.2) or calcium
nitrite (Ca(NO.sub.2).sub.2).
[0025] Alternatively, a nitrite precursor may be used as the source
of the nitrite ions in the composition. Other sources of nitrite
ions are nitrate ions derived from alkali metal or alkaline earth
metal salts capable of enzymic conversion to nitrite. For example,
LiNO.sub.3, NaNO.sub.3, KNO.sub.3, RbNO.sub.3, CsNO.sub.3,
FrNO.sub.3, Be(NO.sub.3).sub.2, Mg(NO.sub.3).sub.2,
Ca(NO.sub.3).sub.2, Sr(NO.sub.3).sub.2, Ba(NO.sub.3).sub.2, or
Ra(NO.sub.3).sub.2.
[0026] The concentration of the nitrate/nitrite ion source in the
layer containing a nitrite may be up to 20% w/w, suitably 0.25 to
15%, suitably 2 to 12%, suitably 4 to 10%, for example 5 to 8%. A
particularly preferred concentration is 6% to 7% w/w.
[0027] Suitably, the final nitrite ion concentration present in the
layer containing a nitrite is up to 20% w/w, generally in the range
of from 0.25% to 15% w/w, for example 0.5% to 14% w/w, 1% to 13%
w/w, suitably 2% to 12% w/w, suitably 3% to 11% w/w, suitably 4 to
10% w/w or 5 to 8% w/w. A particularly preferred nitrite ion
concentration is 6% to 7% w/w.
[0028] If a solution of nitrite ions is being used, the molarity of
the solution is typically from 0.01M to 2M, for example from 0.1M
to 2M, for example from 0.2M to 1.8M, from 0.3M to 1.7M, from 0.4M
to 1.6M, from 0.5M to 1.5M, for example around 0.7M, 0.8M, 0.9M,
1M, 1.1M, 1.2M or 1.3M.
[0029] In one specific embodiment, the first component of the
dressing system is a polypropylene mesh or a plurality of
polypropylene meshes impregnated with sodium nitrite, typically as
a sodium nitrite solution.
[0030] In certain embodiments of the invention, which can
optionally comprise a reductant, the amount (weight or volume) of
nitrite solution can be used to control the amount of nitric oxide
produced over time. Preferred amounts of sodium nitrite solution
are from 5 mg to 100 mg per cm.sup.2 of the area of nitrate
containing layer (for example mesh) in contact with the layer
comprising a source of hydrogen ions, for example from 10 mg to 85
mg per cm.sup.2, from 20 mg to 75 mg per cm.sup.2, from 30 mg to 60
mg per cm.sup.2 or from 10 mg to 85 mg per cm.sup.2. The second
component of the dressing system of the invention provides a source
of hydrogen ions. The second component is therefore acidic.
Hydrogen (H.sup.+) ions can alternatively be referred to as
protons. By virtue of the presence of hydrogen ions, the second
component reduces the pH at the site of application.
[0031] In certain embodiments the second component may be wetted
prior or during use in order to enhance the availability of
hydrogen ions.
[0032] When the second layer is placed in contact with the layer
containing a nitrite, the acidic environment created by the second
component allows the chemical reaction that produces nitric oxide
from nitrite to take place. Thus, when the second layer is placed
in contact with the layer containing a nitrite, nitric oxide is
produced which diffuses through the layer containing a nitrite and
onto or into the skin or wound bed of the patient. It can therefore
be seen that the two components of the system of the invention are
typically kept apart until use, to prevent nitric oxide from being
generated prematurely. In accordance with the present invention, a
minimal amount of nitrogen dioxide is produced as a by-product of
the reaction.
[0033] Without wishing to be bound by theory, when the layer
comprising a source of hydrogen ions is placed on top of the first
component of the system (the layer or layers containing a nitrite),
hydrogen ions are released and diffuse down a concentration
gradient through the layer comprising a source of hydrogen ions and
into the layer containing a nitrite, where they react with the
nitrite to produce nitric oxide. A second process occurs where the
nitrite solution or layer containing the nitrite is absorbed by the
layer containing a source of hydrogen ions and the reaction takes
place at the surface of or within the interface between the layers:
the nitric oxide is released through the layer containing the
nitrite into the tissue. The two components of the system therefore
form a heterogeneous reaction system where they come into contact
with one another. The meaning of a heterogeneous reaction system
will be clear to the skilled reader, but it is important to note
that it is distinct from a homogenous system (i.e., a system where
all components and reactants are mixed). Without wishing to be
bound by theory, the inventors believe the heterogeneous reaction
system formed at the interface of the two layers contributes to the
surprisingly low amount of NO.sub.2 generated by the system of the
invention. Furthermore, the use of heterogeneous reaction system
generates a surprising amount of HONO, which further contributes to
the production of NO from nitrite. These surprising and unexpected
properties resulting from the use of a heterogeneous reaction
system allow for the use of materials in the layer containing a
source of hydrogen ions which would previously have been considered
unsuitable, while maintaining (or even enhancing) the level of
therapeutic NO produced and minimizing the production of
undesirable NO.sub.2. Until now it was assumed that acidification
of nitrite would give rise to equimolar ratios of NO and
NO.sub.2.
[0034] Suitable materials that may act as the layer comprising a
source of hydrogen ions include, but are not limited to Gelling
fibres e.g. carboxymethyl cellulose, (e.g. Aquacel), alginates and
mixtures thereof, superabsorbent dressings based on sodium
polyacrylate e.g. Sorbion, honey dressings such as manukka honey
based dressings, e.g. based on Active Leptospermum Honey e.g.
Medihoney HCS. In preferred embodiments, the layer comprising a
source of hydrogen ions is not a hydrogel. In other preferred
embodiments, the layer comprising a source of hydrogen ions is not
a hydrogel comprising a copolymerised acidic function into the
polymer network of the hydrogel.
[0035] In certain embodiments the layer comprising a source of
hydrogen ions may be wetted prior to use, i.e., it may be combined
with water.
[0036] When wetted with an aqueous solution, the pH of the layer
comprising a source of hydrogen ions is typically from pH2 to pH6,
for example from pH2.5 to pH5.9, from pH2.6 to pH5.8, from pH2.7 to
pH5.7, from pH2.8 to pH5.6, from pH2.9 to pH5.5, from pH3 to pH5.4,
from pH3.1 to pH5.3, from pH3.2 to pH5.2, from pH3.3 to pH5.1, from
pH3.4 to pH5, from pH3.5 to pH4.9, from pH3.6 to pH4.8, from pH3.7
to pH4.7, from pH3.8 to pH4.6, from pH3.9 to pH4.5, for example
around pH4, pH4.1, pH4.2, pH4.3 or pH4.4. Preferably, the pH of the
layer comprising a source of hydrogen ions is below around 5.5.
[0037] The present invention is derived from have previously
devised a dressing system in which it is preferable for the
pK.sub.a of the monomer or one of the monomers in a hydrogel to be
within 1 unit of the pH of the hydrogel. Such a dressing system is
described in International Application No. PCT/GB2014/051543
(published as WO/2014/188174) and International Application No.
PCTIGB2014/051544 (published as WO/2014/188175), which are
incorporated herein by reference in their entirety.
[0038] The layer comprising a source of hydrogen ions may contain a
pH buffer to maintain the pH in the range 2-4.5. However, the
addition of a pH buffer is typically not required.
[0039] The thickness of the layer comprising a source of hydrogen
ions is typically up to 4 mm, typically 0.5-2 mm, more typically
1-2 mm, even more typically 1-1.6 mm.
[0040] In one embodiment, the layer comprising a source of hydrogen
ions also contains a solid layer within it to provide mechanical
strength, for example for processing purposes. The solid layer can
be made of any suitable material and in one embodiment is a mesh,
suitably made of a polymer, suitably a polypropylene mesh. The
solid layer is suitably provided in the middle of the layer, for
example in the form of a "sandwich" wherein the solid layer is
sandwiched in between two layers of material.
[0041] In one embodiment, the layer comprising a source of hydrogen
ions also has a barrier layer, for example a film such as a
polyurethane film or an adhesive coated polyurethane film, on one
of its external surfaces, typically on the surface that will be
exposed to the air when in use. This layer typically provides a
bacterial barrier. In certain other embodiments, the system may
comprise a third layer, wherein the third layer comprises a barrier
layer, for example a film such as a polyurethane film or an
adhesive coated polyurethane film, on one of its external surfaces,
typically on the surface that will be exposed to the air when in
use. This third layer comprising a barrier layer would then a
bacterial barrier. Preferably, the third layer is placed on top of
the other layers of the system.
[0042] In one embodiment, the system of the first aspect of the
invention further contains a pharmaceutically active agent. In this
embodiment, the NO produced by the system is used to deliver the
pharmaceutically active agent transdermally. The pharmaceutically
active agent may be present either in the layer containing a
nitrite or in the layer comprising a source of hydrogen ions.
[0043] If the pharmaceutically active agent is present in the layer
containing the nitrite, the layer is typically imbibed or
impregnated with the pharmaceutically active agent, for example by
soaking the layer in a solution of the pharmaceutically active
agent. This can be done at the same time as imbibing or
impregnating the layer with the nitrite. For example, the layer can
be soaked in a solution comprising a mixture of a nitrite and the
pharmaceutically active agent for this purpose.
[0044] If the pharmaceutically active agent is present in the layer
comprising a source of hydrogen ions, the pharmaceutically active
agent is typically incorporated into the layer, or is present on
the surface of the layer, in any suitable format.
[0045] When it contains a pharmaceutically active agent, the system
of the invention can be used for the transdermal delivery of any
pharmaceutically active agent.
[0046] The pharmaceutically active agent may comprise any suitable
drug or combination of drugs to treat a disease in a patient. The
agent may be immediately active in the form administered or may
become active in the body of the patient following administration,
such as for example through hydrolysis or by the action of an
endogenous enzyme.
[0047] Therapeutically, the system of the invention can facilitate
the delivery of a wide number of systemically active substances.
Active substances include, but are not limited to, antibiotics,
hormones, proteins, peptides, proteoglycans, nucleotides,
oligonucleotides (such as DNA, RNA, etc.), vitamins, minerals,
growth factors, non-steroidal anti-inflammatory drugs (NSAIDs) and
vaccines. In certain embodiments the active substance may be an
antimicrobial agent. Antimicrobial agents include, but are not
limited to, Silver, Octenidine, Chlorhexidine gluconate, and
Iodine. In a preferred embodiment, the delivery system of the
present invention can be used to deliver anaesthetic, analgesic,
hormone, immunosuppressant or steroid formulations. Other
pharmaceutical agents include, but are not limited to, analgesic
agents such as ibuprofen, indomethacin, diclofenac, acetylsalicylic
acid, paracetamol, propranolol, metoprolol, oxycodone, thyroid
releasing hormone, sex hormones such as oestrogen, progesterone and
testosterone, insulin, verapamil, vasopressin, hydrocortisone,
scopolamine, nitroglycerine, isosorbide dinitrate, anti-histamines
(such as terfenadine), clonidine and nicotine, non-steroidal
immunosuppressant drugs (such as cyclosporin, methotrexate,
azathioprine, mycophenylate, cyclophosphamide, TNF antagonists),
anticonvulsants and other drugs for
dementia/Alzheimer's/Parkinson's disease such as apamorphone and
rivastigmine, and steroids.
[0048] Typically, the pharmaceutically active agent is an
anaesthetic. The anaesthetic can be any appropriate anaesthetic for
local anaesthesia and can be provided in aqueous or powdered form,
for example, lignocaine (lidocaine), amethocaine (tetracaine),
xylocaine, bupivacaine, prilocaine, ropivacaine, benzocaine,
mepivocaine or cocaine, or a mixture thereof, preferably in the
hydrochloride form.
[0049] The general concentration range is around 1 to 4%, up to 10%
w/w, although greater or lesser amounts can be empirically
determined by a physician. Suitably preferred concentrations are
tetracaine (0.01 to 10% w/w, suitably 1 to 8% w/w, preferably 2%
w/w), lidocaine (0.01 to 10% w/w, suitably 1 to 8% w/w, preferably
5% or 10% w/w) and cocaine (1 to 4% w/w). Generally accepted safe
dosages of such compounds for topical anaesthesia in a healthy 70
kg-adult are 750 mg for lidocaine, 200 mg for cocaine, and 50 mg
for tetracaine. Other suitable anaesthetics are within the
competence of the medical practitioner and can also be used in the
system of the present invention at the relevant concentrations.
[0050] Prior art methods of improving local anaesthesia have
suggested the use of low concentrations of vasoconstrictors, such
as phenylephrine (0.005%). However, the compositions of the present
invention utilise a previously unknown property of an acidified
nitrite composition to produce NO, a vasodilator, which accelerates
the transfer of anaesthetic into the dermis. The combination of the
NO-generating system and anaesthetic will promote patient
compliance of venepuncture and bloodletting techniques by reducing
the pain experienced during the procedure and reducing associated
infection.
[0051] The choice of pharmaceutically active agent may be
determined by its suitability for the treatment regimen of the
disease or medical condition concerned and reference can be made to
standard reference works such as Martindale, the Merck Index,
Goodman & Gilman's "The Pharmacological Basis of Therapeutics",
10th edition (2001), McGraw Hill and the British National Formulary
(http://www.bnf.org/bnf/index.htm).
[0052] It should be emphasised that when it contains a
pharmaceutically active agent the system of the invention is
typically used to deliver a pharmaceutically active agent other
than nitric oxide, i.e. the pharmaceutically active agent is not
nitric oxide.
[0053] In use, the second component of the dressing system
(containing a source of hydrogen ions) is placed on top of the
first component of the dressing system (the layer containing a
nitrite). The second component has a number of functions. Firstly,
by virtue of the presence of hydrogen ions that are released from
this component, the second component creates an acid environment
for the conversion of nitrite to nitric oxide. Also, the second
component of the dressing system is typically larger than the first
component, and is of a suitable size and shape that when it
overlays the first component it entirely covers the first
component, such that there is an area on one or more of its edges,
and typically all the way round the first component, that is in
contact with the skin of the patient (although the second component
is typically not in contact with a wound; rather, the first
component of the dressing system is typically in contact with a
wound when the dressing system is a wound dressing system). The
second component may be adhesive and so, in this configuration, the
second component retains the first component in place on the skin
of a patient, typically over an ulcer or wound, in a manner
analogous to that of a plaster (or BandAid.TM.).
[0054] Since the system of the invention is a dressing useful, for
example, for the treatment of ulcers and wounds, it is adapted for
transdermal administration. The components of the system of the
invention may be prepared by any method known in the art of
pharmacy, and are typically prepared under sterile conditions.
[0055] The system of the invention is a two component system,
comprising a first component which comprises a layer or a plurality
of layers containing a nitrite and a second component comprising a
source of hydrogen ions. In one embodiment, the system of the
invention does not contain any other components. In this
embodiment, the system consists of or consists essentially of a
first component which comprises a layer or a plurality of layers
containing a nitrite and a second component comprising a source of
hydrogen ions. In one embodiment, the first component consists of
or consists essentially of a (typically permeable) layer or
plurality of layers containing a nitrite. In another embodiment,
the second component consists of or consists essentially of a
source of hydrogen ions.
[0056] The system of the invention typically does not contain
certain other substances. In particular, the system itself or one
or both of its components typically does not contain a thiol and/or
a reductant, typically a non-thiol reductant, or only contains
these substances in trace amounts, i.e. less than 0.05%, typically
less than 0.01%, more typically less than 0.005% by weight of the
system, or one or both components thereof. Thiols include
glutathione (typically L-glutathione), 1-thioglycerol,
1-thioglucose, cysteine, and methyl- or ethyl-ester of cysteine,
N-acetylcysteine, mercaptoethylamine and 3-mercaptopropanoic acid.
Non-thiol reductants include iodide anion, butylated hydroquinone,
tocopherol, butylated hydroxyanisole, butylated hydroxytoluene and
beta-carotene, erythrobate or .alpha.-tocopherol, ascorbic acid
(vitamin C). In some embodiments, the system itself or one or both
of its components does not contain a source of Cu.sup.2+ Zn.sup.2+
and/or Fe.sup.2+ ions.
[0057] In one embodiment, the first component does not contain a
thiol and/or a reductant, typically a non-thiol reductant. In
another embodiment, the second component does not contain a thiol
and/or a reductant, typically a non-thiol reductant. In another
embodiment, both the first component and the second component do
not contain a thiol and/or a reductant, typically a non-thiol
reductant.
[0058] In one embodiment, the first component does not contain a
source of Cu.sup.2+ Zn.sup.2+ and/or Fe.sup.2+ ions. In another
embodiment, the second component does not contain a source of Cu
.sup.2+ Zn.sup.2+ and/or Fe.sup.2+ ions. In another embodiment,
both the first component and the second component do not contain a
source of Cu.sup.2+ Zn.sup.2+ and/or Fe.sup.2+ ions.
[0059] The dressing system of the invention has either (a) two
active components: the layer comprising a source of hydrogen ions
and the layer containing a nitrite; or (b) three active components:
the layer comprising a source of hydrogen ions, the layer
containing a nitrite and a pharmaceutically active agent. No other
active components are necessary for the functioning of the dressing
system of the present invention.
[0060] The present inventors have now surprisingly found that the
use of a heterogeneous reaction system is advantageous as it limits
the amount of NO.sub.2 by-product in the reaction that occurs to
produce NO. This is demonstrated in the Examples of the present
application.
[0061] In a second aspect, the present invention provides the
system of the first aspect of the invention for use in
medicine.
[0062] In a third aspect, the present invention provides the system
of the first aspect of the invention for use in the treatment of a
condition associated with tissue ischaemia or a wound. This aspect
of the invention also extends to the use of a layer containing a
nitrite and a layer comprising a source of hydrogen ions in the
manufacture of a medicament for the treatment of a condition
associated with tissue ischaemia or a wound.
[0063] This aspect of the invention also extends to:
[0064] A layer containing a nitrite for use in the treatment of a
condition associated with tissue ischaemia or a wound, wherein said
layer is administered simultaneously, separately or sequentially
with a layer comprising a source of hydrogen ions.
[0065] A layer comprising a source of hydrogen ions for use in the
treatment of a condition associated with tissue ischaemia or a
wound, wherein said layer is administered simultaneously,
separately or sequentially with a layer containing a nitrite.
[0066] Use of a layer containing a nitrite in the manufacture of a
medicament for the treatment of a condition associated with tissue
ischaemia or a wound, wherein said layer is administered
simultaneously, separately or sequentially with a layer comprising
a source of hydrogen ions.
[0067] Use of a layer comprising a source of hydrogen ions in the
manufacture of a medicament for the treatment of a condition
associated with tissue ischaemia or a wound, wherein said layer is
administered simultaneously, separately or sequentially with a
layer containing a nitrite.
[0068] A system comprising a layer containing a nitrite and a layer
comprising a source of hydrogen ions as a combined preparation for
simultaneous, separate or sequential use in treating a condition
associated with tissue ischaemia or a wound.
[0069] This aspect of the invention also extends to a method of
treatment of a condition associated with tissue ischaemia or a
wound comprising administering a system of the first aspect of the
invention to a subject in need thereof. The subject is a patient
having a condition associated with tissue ischaemia or a wound, as
described herein. The method typically comprises administering to
the patient the first component described herein and then
subsequently administering the second component described herein,
on top of the first component. Tissue ischaemia is a restriction of
the blood supply to tissues. In some embodiments, the tissue
ischaemia is peripheral ischaemia, i.e. where peripheral
circulation is restricted, for example skin ischaemia.
[0070] In some circumstances, damage to the skin leads to tissue
ischaemia as the blood supply is reduced or prevented by the body's
own repair or defence mechanisms.
[0071] Conditions associated with tissue ischaemia include
Raynaud's syndrome, severe primary vasospasm and tissue ischaemia
caused by septic shock or irradiation or a peripheral vascular
disease (for example caused by diabetes and other chronic/systemic
diseases), as well as post-surgical tissue ischaemia.
[0072] The present invention is also useful in the treatment of
wounds. Wounds include ulcers, skin donor sites, surgical wounds
(post-operative), burns (for example scalds, superficial, partial
thickness and full thickness burns), lacerations and abrasions, and
can be chronic or acute. Some burns (for example full thickness and
some partial thickness burns) are also associated with tissue
ischaemia. Ulcers can be of various origin, for example of venous
or arterial origin, and include leg ulcers, pressure ulcers, venous
ulcers and ulcers associated with diabetes such as diabetic foot
ulcers. The present invention is also useful in the treatment of
wounds that are infected.
[0073] Dosages of nitric oxide, which is the active substance
produced by the system of the present invention when it does not
contain an additional pharmaceutically active agent, can vary
between wide limits, and can be tailored depending upon the disease
or disorder to be treated, the severity of the condition, and the
age and health of the individual to be treated, etc. A physician
will ultimately determine appropriate dosages to be used. The
system is configured so as to deliver nitric oxide in a
therapeutically active amount, which is an amount that ameliorates
or eliminates the symptoms of the condition (such as an ulcer or
wound) that is being treated. As described herein, the system of
the present invention can be used to control the amount and
duration of nitric oxide release.
[0074] This dosage may be repeated as often as appropriate. If side
effects develop the amount and/or frequency of the dosage can be
reduced or otherwise altered or modified, in accordance with normal
clinical practice.
[0075] The system of the invention may be formulated for use in
human or for veterinary medicine. The present application should be
interpreted as applying equally to humans as well as to animals,
unless the context clearly implies otherwise.
[0076] In a fourth aspect, the present invention provides a kit
comprising a layer containing a nitrite and a layer comprising a
source of hydrogen ions as a combined preparation for simultaneous,
separate or sequential use in treating a condition associated with
tissue ischaemia or a wound. The kit is suitably provided with
instructions for use in the treatment of a condition associated
with tissue ischaemia or a wound.
[0077] When the system of the first aspect of the invention also
comprises a pharmaceutically active agent, the invention also
extends to the use of such a system for the treatment of a disease
or condition other than a condition associated with tissue
ischaemia or a wound.
[0078] Accordingly, in a fifth aspect, the present invention
provides the system of the first aspect of the invention comprising
a pharmaceutically active agent for use in the treatment of a
disease or medical condition. Medical conditions that can be
treated using the system of the present invention comprising a
pharmaceutically active agent include pain, wherein the system of
the invention is used to provide local anaesthesia, and transplant
rejection, wherein the system of the invention is used to provide
the effect of immunosuppression. Pain includes chronic and acute
pain, post-operative pain and neuropathic pain. Diseases suitable
for treatment using the system of the present invention comprising
a pharmaceutically active agent include but are not limited to
cardio-vascular diseases, neurological diseases or disease of the
central nervous system, (e.g. multiple sclerosis, Parkinson's
Disease), epilepsy, psychiatric disorders (e.g. schizophrenia),
inflammation (e.g. rheumatoid arthritis, osteoarthritis, asthma,
gout), in particular topical inflammation, hypertension,
arrhythmia, hyperlipoproteinemias, gastrointestinal disorders (e.g.
peptic ulcers), kidney disease, parasite infections (e.g. protozoal
infection, helminthiasis, amebiasis, giardiasis, thichomoniasis,
leishmaniasis, trypanosomiasis, malaria), microbial infection (e.g.
yeast, fungus, bacteria), viral infection, cancer,
immunosuppression, blood disorders (blood clots etc.), endocrine
(e.g. hormonal) disorders (e.g. thyroid condition, hypoglycaemia),
diabetes, dermatological disorders (e.g. psoriasis). It will be
understood that the disease to be treated using the system of the
invention will depend on the nature of the pharmaceutically active
agent that to be delivered transdermally using the system of the
present invention.
[0079] In one embodiment, the present invention provides the system
of the first aspect of the invention for use in the treatment of
pain, wherein the pharmaceutically active agent is an anaesthetic
selected from the group consisting of lignocaine (lidocaine),
amethocaine (tetracaine), xylocaine, bupivacaine, prilocaine,
ropivacaine, benzocaine, mepivocaine, cocaine or a mixture thereof.
In this embodiment, the treatment of pain is typically local
anaesthesia.
[0080] This aspect of the invention also extends to the use of a
layer containing a nitrite and a layer comprising a source of
hydrogen ions in the manufacture of a medicament for the treatment
of a disease or medical condition, wherein the layer containing a
nitrite and/or the layer comprising a source of hydrogen ions
comprises a pharmaceutically active agent. In particular, this
aspect of the invention extends to the use of a layer containing a
nitrite and a layer comprising a source of hydrogen ions in the
manufacture of a medicament for the treatment of pain, wherein the
layer containing a nitrite and/or the layer comprising a source of
hydrogen ions comprises a pharmaceutically active agent and wherein
the pharmaceutically active agent is an anaesthetic selected from
the group consisting of lignocaine (lidocaine), amethocaine
(tetracaine), xylocaine, bupivacaine, prilocaine, ropivacaine,
benzocaine, mepivocaine, cocaine or a mixture thereof.
[0081] This aspect of the invention also extends to:
[0082] A layer containing a nitrite for use in the treatment of a
disease or condition, wherein said layer is administered
simultaneously, separately or sequentially with a layer comprising
a source of hydrogen ions, wherein the layer containing a nitrite
and/or the layer comprising a source of hydrogen ions comprises a
pharmaceutically active agent.
[0083] A layer comprising a source of hydrogen ions for use in the
treatment of a disease or condition, wherein said layer is
administered simultaneously, separately or sequentially with a
layer containing a nitrite, wherein the layer containing a nitrite
and/or the layer comprising a source of hydrogen ions comprises a
pharmaceutically active agent.
[0084] Use of a layer containing a nitrite in the manufacture of a
medicament for the treatment of a disease or condition, wherein
said layer is administered simultaneously, separately or
sequentially with a layer comprising a source of hydrogen ions,
wherein the layer containing a nitrite and/or the layer comprising
a source of hydrogen ions comprises a pharmaceutically active
agent.
[0085] Use of a layer comprising a source of hydrogen ions in the
manufacture of a medicament for the treatment of a disease or
condition, wherein said layer is administered simultaneously,
separately or sequentially with a layer containing a nitrite,
wherein the layer containing a nitrite and/or the layer comprising
a source of hydrogen ions comprises a pharmaceutically active
agent.
[0086] A system comprising (i) a layer containing a nitrite and
(ii) a layer comprising a source of hydrogen ions as a combined
preparation for simultaneous, separate or sequential use in
treating a disease or condition, wherein the layer containing a
nitrite and/or the layer comprising a source of hydrogen ions
comprises a pharmaceutically active agent.
[0087] In this aspect of the invention, the disease or condition is
typically pain and the pharmaceutically active agent is an
anaesthetic selected from the group consisting of lignocaine
(lidocaine), amethocaine (tetracaine), xylocaine, bupivacaine,
prilocaine, ropivacaine, benzocaine, mepivocaine, cocaine or a
mixture thereof.
[0088] This aspect of the invention also extends to a method of
treatment of a disease or condition comprising administering a
system of the first aspect of the invention comprising a
pharmaceutically active agent to a subject in need thereof. The
method typically comprises administering to the patient the first
component described herein and then subsequently administering the
second component described herein, on top of the first component.
The subject is typically a patient suffering from pain. In this
embodiment, the pharmaceutically active agent is typically an
anaesthetic selected from the group consisting of lignocaine
(lidocaine), amethocaine (tetracaine), xylocaine, bupivacaine,
prilocaine, ropivacaine, benzocaine, mepivocaine, cocaine or a
mixture thereof.
[0089] Dosages of the pharmaceutically active agent that is
delivered by in this embodiment of the system of the present
invention can vary between wide limits, depending upon the disease
or disorder to be treated, the severity of the condition, and the
age and health of the individual to be treated, etc. and a
physician will ultimately determine appropriate dosages to be used.
The system is configured so as to deliver the pharmaceutically
active agent in a therapeutically active amount, which is an amount
that ameliorates or eliminates the symptoms of the disease or
disorder that is being treated.
[0090] In a sixth aspect, the present invention provides a kit
comprising (i) a layer containing a nitrite, and (ii) a layer
comprising a source of hydrogen ions as a combined preparation for
simultaneous, separate or sequential use in treating a disease or
condition wherein the layer containing a nitrite and/or the layer
comprising a source of hydrogen ions comprises a pharmaceutically
active agent. The disease or condition is typically pain and the
pharmaceutically active agent is typically an anaesthetic selected
from the group consisting of lignocaine (lidocaine), amethocaine
(tetracaine), xylocaine, bupivacaine, prilocaine, ropivacaine,
benzocaine, mepivocaine, cocaine or a mixture thereof. The kit is
suitably provided with instructions for use in the treatment of the
disease or condition.
[0091] The present inventors have also previously found that when
applied as a pre-treatment, a dressing system of the invention
functions to increase the effectiveness of a topically applied
aqueous-soluble anaesthetic. The system of the invention can
therefore also be used in combination with an aqueous-soluble drug
such as an anaesthetic when the dressing system is administered
simultaneously with the drug (such as an anaesthetic) or before or
after the drug (such as an anaesthetic). In this aspect of the
invention, the dressing system of the first aspect of the invention
does not include a pharmaceutically active agent; the
aqueous-soluble drug is administered separately from the dressing
system.
[0092] Accordingly, in a seventh aspect, the present invention
provides the system of the first aspect of the invention in
combination with an aqueous-soluble drug for use in medicine.
[0093] By "aqueous-soluble drug" is meant one that for each part of
the drug will require 1000 parts or less of an aqueous solvent to
solubilise it. In other words, the drug is at least slightly
soluble in accordance with the definition given in The United
States Pharmacopeia, USP 30-NF 25, 2007 arid British Pharmacopoeia,
2009. For example, lidocaine hydrochloride is soluble on this scale
requiring 20 parts water to 1 part lidocaine.
[0094] Examples of aqueous-soluble drugs for use in accordance with
this aspect of the invention include the anti-hypertensive,
Atenolol, the water soluble antibiotics, Ampicillin, Streptomycin,
Penicillin and the naturally water-soluble vitamins, specifically B
and C.
[0095] In an eighth aspect, the present invention provides the
system of the first aspect of the invention in combination with an
anaesthetic for use in the treatment or prevention of pain.
[0096] The anaesthetic can be any appropriate anaesthetic for local
anaesthesia and is typically selected from the group consisting of
lignocaine (lidocaine), amethocaine (tetracaine), xylocaine,
bupivacaine, prilocaine, ropivacaine, benzocaine, mepivocaine,
cocaine or a mixture thereof. The anaesthetic is typically provided
in aqueous or powdered form. For example, anaesthetics such as
lidocaine hydrochloride can be provided in the form of a spray of
the drug in aqueous form.
[0097] The treatment or prevention of pain is typically local
anaesthesia but can be the treatment or prevention of any kind of
pain. Pain includes chronic and acute pain, post-operative pain and
neuropathic pain. Treatment includes both amelioration and
prevention (prophylaxis) of pain.
[0098] The general concentration range is around 1 to 4%, up to 10%
w/w, although greater or lesser amounts can be empirically
determined by a physician. Suitably preferred concentrations are
tetracaine (0.01 to 10% w/w, suitably 1 to 8% w/w, preferably 2%
w/w), lidocaine (0.01 to 10% w/w, suitably 1 to 8% w/w, preferably
5% or 10% w/w) and cocaine (1 to 4% w/w). Generally accepted safe
dosages of such compounds for topical anaesthesia in a healthy 70
kg-adult are 750 mg for lidocaine, 200 mg for cocaine, and 50 mg
for tetracaine. Other suitable anaesthetics are within the
competence of the medical practitioner and can also be used in the
system of the present invention at the relevant concentrations.
[0099] This aspect of the invention also extends to:
[0100] A system of the first aspect of the invention for use in the
treatment or prevention of pain, wherein said system is
administered simultaneously, separately or sequentially with an
anaesthetic.
[0101] Use of a system of the first aspect of the invention in the
manufacture of a medicament for the treatment or prevention of
pain, wherein said system is administered simultaneously,
separately or sequentially with an anaesthetic.
[0102] This aspect of the invention also extends to a method of
treatment or prevention of pain comprising administering a system
of the first aspect of the invention and an anaesthetic to a
subject in need thereof.
[0103] The subject is a patient suffering from pain, or one who is
likely to suffer from pain in the future (and therefore is in need
of anaesthetic). The method typically comprises either
administering to the patient the system of the first aspect of the
invention (as a pre-treatment) and then subsequently administering
an aqueous-soluble drug such as an anaesthetic, or administering to
the patient an aqueous-soluble drug such as an anaesthetic and then
subsequently administering the patient the system of the first
aspect of the invention. Alternatively, the system of the first
aspect of the invention and the aqueous-soluble drug such as an
anaesthetic are administered simultaneously.
[0104] Preferred features for the second and subsequent aspects of
the invention are as for the first aspect mutatis mutandis.
[0105] The present invention will now be described by way of
illustration only with reference to the following Examples and
Figures, in which:
[0106] FIG. 1 shows a plot of results for analysis of HONO using 1
quarter dressing (4 repeats) at 660 mL/min flow rate with synthetic
air (A); and a plot of results for analysis of HONO using 1 quarter
dressing (4 repeats) at 660 mL/min flow rate with synthetic air
rescaled for baseline comparison (B).
[0107] FIG. 2 shows plot of results for analysis of NO using 1
quarter dressing (4 repeats) at 660 mL/min flow rate with synthetic
air rescaled (A); and plot of results for analysis of NO using 1
quarter dressing (4 repeats) at 660 mL/min flow rate with synthetic
air rescaled for baseline comparison (B).
[0108] FIG. 3 shows plot of results for NO.sub.2 analysis using 1
quarter dressing (4 repeats) at 660 mL/min flow rate using
synthetic air.
[0109] FIG. 4 shows a plot of results for dressing analysis,
dressing 1 at 660 mL/min air flow rate, concentration in
nmol/mL.
[0110] FIG. 5 shows a plot of results for dressing analysis,
dressing 2 at 660 mL/min air flow rate, concentration in
nmol/mL.
[0111] FIG. 6 shows a plot of results for dressing analysis,
dressing 3 at 660 mL/min air flow rate, concentration in
nmol/mL.
[0112] FIG. 7 shows a plot of results for dressing analysis,
dressing 4 at 660 mL/min air flow rate, concentration in
nmol/mL.
[0113] FIG. 8 shows a plot for a dressing analysis, quarter
dressing at the 50 mL/min synthetic air flow rate.
[0114] FIG. 9 a plot for a dressing analysis of the full dressing
stuck over sampling tube (A) and a plot for a dressing analysis for
a quarter dressing face down over sampling tube (B).
[0115] FIG. 10 shows the output from SIFT-MS over time for a
nitrite mesh/Aquacel system. As can be seen, the production of NO
is favourable compared to NO.sub.2 and HNO.sub.2 production.
[0116] FIG. 11 shows the output from SIFT-MS over time for a
nitrite mesh/Medihoney HCS system. As can be seen, the production
of NO is favourable compared to NO.sub.2 and HNO.sub.2
production.
EXAMPLE 1
Selected Ion Flow Tube Mass Spectrometry Analysis of Nitric Oxide
Generating Wound Dressing
[0117] The production of NO, NO.sub.2 and HNO.sub.2 by a dressing
based on a hydrogel system (as described in WO/2014/188174) was
tested using Selected Ion Flow Tube Mass Spectrometry
(SIFT-MS).
[0118] Method
[0119] The SIFT-MS system was calibrated for the detection of the
compounds of interest using reference samples.
[0120] The compounds generated by the dressing system were then
tested in a flow cell set up. Briefly, a 670 mL plastic (BPA free)
clip lock tub with silicone seal (Tesco) was used and cleaned with
low concentration of Virkon detergent before being rinsed with
deionised water and dried with paper towel. Two holes were drilled
one on either side, one for synthetic air in and one for sample air
out. Synthetic air from the cylinder (BOC, the Linde group)
(<0.1 parts per million (ppm) NOx) flowed into the chamber
whilst a NMPO5B micro-pump (KNF Neuberger U.K. Ltd) draws the
sample air out of the chamber over the SIFT-MS inlet capillary. The
flow rate of air into the chamber was set according to the
experiment (either 50 mL/min or 660 mL/min) and sample air was
drawn over the capillary at the set flow rate, depending on the
experiment (N.B. the SIFT-MS draws air through the capillary at a
constant rate of 2.7 mL per minute). In order to achieve higher
flow rates two pumps were required. Table 1 shows the various
permutations of the undertaken analysis;
TABLE-US-00001 TABLE 1 showing the various permutations of analysis
carried out. Dressing Dressing size Air Flow Pump flow Position
Analyte Repeats 2.5 .times. 2.5/5 .times. 5 50 mL/min 50 mL/min
Face up NO/NO.sub.2 2 2.5 .times. 2.5/5 .times. 5 50 mL/min 50
mL/min Face up HONO 2 2.5 .times. 2.5/5 .times. 5 None None Face
down NO/NO.sub.2 1 2.5 .times. 2.5/5 .times. 5 None None Face down
HONO 1 Full dressing 50 mL/min 50 mL/min Face up NO/NO.sub.2 1 Full
dressing 50 mL/min 50 mL/min Face up HONO 1 Full dressing None None
Face down NO/NO.sub.2 1 Full dressing 50 mL/min 50 mL/min Face up
HONO 1 Full dressing None None Face down HONO 1 Full dressing 660
mL/min 660 mL/min Face up NO/NO.sub.2 2 Full dressing 660 mL/min
660 mL/min Face up HONO 2 2.5 .times. 2.5/5 .times. 5 660 mL/min
660 mL/min Face up NO/NO.sub.2 4 2.5 .times. 2.5/5 .times. 5 660
mL/min 660 mL/min Face up HONO 4
[0121] All the dressings were treated in the same way; the layers
were combined as quickly as possible before the chamber was sealed,
though no significant delays were noted it is possible there may
have been a few seconds difference between the dressing being
combined and the sealing of the chamber. Dressing LOT numbers
D0207150/D0305150.
[0122] Analysis
[0123] The data from the quarter dressing at the 660 mL/min flow
rate was converted into excel data. This was used to generate one
graph for each dressing showing the production of all three target
analytes; and one graph per analyte comparing all four dressings
(see results). Duplicate graphs were created with only visible
trend lines which have been created using a 25 point moving average
in order to smooth out the results by reducing the noise, this step
proved useful for performing visual analysis.
[0124] Each compound for each dressing was also converted into
micrograms (pg) per minute evolved both over the course of the
testing duration (1.5 hours) and for the initial 15 minutes (to
encompass the initial peak). This was then used to calculate the
total quantities in .mu.g for the respective time frames.
[0125] Results
[0126] The following shows the results for the face up, quarter
dressing at the 660 mL/min flow rate method. Four analyses for each
analyte were performed using different dressings. Table 2 below
shows the quantities calculated for the four different
dressings.
TABLE-US-00002 TABLE 2 quantification of the compounds evolved from
each dressing, each analysis performed with same method. 1 quarter
dressing with 660 mL/min flow rate using synthetic air. Dress-
Dress- Dress- Dress- ing 1 ing 2 ing 3 ing 4 Total AverageHONO
(ppm) 4.23 2.47 2.18 3.18 Average first 15 minutes 17.20 9.94 8.43
12.65 MONO (ppm) Amount evolved .mu.g/min 5.28 3.09 2.72 3.97 total
HONO Amount evolved .mu.g/min 21.47 12.40 10.52 15.79 first 15 mins
HONO Total HONO evolved .mu.g 474.89 277.94 244.42 357.44 Total
HONO evolved first 322.05 186.07 157.77 236.84 15 min (.mu.g) Total
Average NO (ppm) 7.70 9.60 6.54 7.79 Average NO first 28.00 37.78
25.73 28.72 15 minutes (ppm) Amount NO 6.12 7.62 5.19 6.18 evolved
.mu.g/min total Amount NO 22.23 30.00 20.43 22.80 evolved .mu.g/min
first 15 mins Total NO evolved 550.44 686.05 467.04 556.34 .mu.g
Total NO evolved 333.50 449.93 306.41 342.07 first 15 min (.mu.g)
Total Average 0.41 0.41 0.38 0.41 NO.sub.2 (ppm) Average NO.sub.2
first 0.26 0.37 0.30 0.29 15 minutes (ppm) Amount NO.sub.2 0.49
0.50 0.46 0.50 evolved .mu.g/min total Amount NO.sub.2 0.32 0.45
0.36 0.35 evolved .mu.g/min first 15 mins Total NO.sub.2 evolved
44.55 45.01 41.48 44.88 .mu.g Total NO.sub.2 evolved first 4.74
6.71 5.42 5.28 15 min (.mu.g)
TABLE-US-00003 TABLE 3 the total quantity of measured compounds
released over the course of 90 minutes and during the first fifteen
minutes, for each dressing, i.e. The value is the result of HONO,
NO, NO.sub.2 production added together. Dress- Dress- Dress- Dress-
ing 1 ing 2 ing 3 ing 4 Total production (.mu.g) 1069.88 1009
752.94 958.66 Total production first 15 mins 660.29 642.71 469.6
584.19 (.mu.g) Total dressing production - 832.73 726.85 547.74
759.76 total empty chamber production (over 90 mins) (.mu.g) Total
dressing production - 620.77 595.68 435.4 551.04 total empty
chamber production (first 15 mins) (.mu.g)
TABLE-US-00004 TABLE 4 quantity of HONO, NO and NO.sub.2 produced
by the empty chamber sealed over a 120 second sampling time using
synthetic air at a flow rate of 660 mL/min. Pre-Dres- Pre-Dres-
Pre-Dres- Pre-Dres- sing 1 sing 2 sing 3 sing analysis analysis
analysis 4 analysis Total Average HONO 0.21 0.32 0.15 0.14 (ppm)
Amount evolved 0.26 0.40 0.19 0.17 .mu.g/min total HONO Total HONO
evolved 0.53 0.80 0.39 0.34 .mu.g Total Average NO 2.38 2.94 1.91
1.85 (ppm) Amount NO evolved 1.89 2.34 1.52 1.47 .mu.g/min total
Total NO evolved .mu.g 3.81 4.71 3.07 2.97 Total Average NO.sub.2
0.38 0.31 0.45 0.45 (ppm) Amount NO.sub.2 evolved 0.46 0.38 0.54
0.55 .mu.g/min total Total NO.sub.2 evolved .mu.g 0.93 0.76 1.10
1.11 Total evolved over 5.27 6.27 4.56 4.42 120 seconds (.mu.g)
Total evolved over 237.15 282.15 205.2 198.9 1.5 hours (same as
sample time)(.mu.g) Total evolved over 39.53 47.03 34.2 33.15 first
15 minutes .mu.g
TABLE-US-00005 TABLE 5 showing quantification for each compound in
nmol. Dres- Dres- Dres- Dres- sing 1 sing 2 sing 3 sing 4 HONO
Total average 0.173 0.101 0.064 0.093 nmol/mL per second HONO total
average 10.375 6.075 3.816 5.582 nmol/mL per min Total amount
evolved 933.714 546.776 343.410 502.390 nmol 90 mins NO total
average 0.315 0.392 0.267 0.318 nmol/mL per second NO total average
18.883 23.506 16.033 19.102 nmol/mL per min Total amount evolved
1699.456 2115.520 1442.926 1719.174 nmol 90 min NO.sub.2 total
average 0.016 0.017 0.015 0.017 nmol/mL per second NO.sub.2 total
average 0.990 1.002 0.924 0.997 nmol/mL per minute NO.sub.2 total
evolved 89.068 90.176 83.147 89.757 nmol 90 mins
[0127] In order to obtain the .mu.g per minute value the following
calculations took place. The molecular weight of the compound at an
assumed temperature of 299K was used to calculate the mass per
cm.sup.3 (1.222 mg for NO). This was then multiplied by the flow
rate (average of 650 mL/min) to arrive at 794 mg per minute, for
100% NO i.e. 106 ppm. Thus the equation to convert ppm into mg per
minute for NO was therefore 794*(X/10.sup.6)=mg per minute (where X
is the ppm). In order to use uniform significant figures milligrams
were converted to micrograms. The same formulae with appropriate
coefficients were applied to all three compounds e.g.
1222*(X/10.sup.6) for NO.sub.2 and 1248*(X/10.sup.6) for HONO.
[0128] Dressing 3 appears to be an outlier with less production of
all three compounds than the other dressings. Excluding dressing 3
the quantities for HONO and NO production shown in table 2 appear
to follow an inverse correlation, the dressing with the highest NO
value over 1.5 hours also has the lowest HONO value (dressing 2).
Likewise the highest HONO producer shows the lowest NO production
(dressing 1). This is likely indicative of the conversion of HONO
into NO. NO.sub.2 appears to have no such relationship with the
other compounds produced as the readings were remarkably similar
for all 4 dressings.
[0129] Table 4 shows the production of HONO, NO and NO.sub.2 over
120 seconds with air flow into the sealed chamber before the
dressing was added to act as a baseline level. As the sealed
chamber with synthetic air flow was not recorded for the same
duration as the dressing the average production over the course of
120 seconds was used to calculate the average production over 1.5
hours (the same as testing time). It is worth noting the average
production, in ppm is significantly less than seen in table 2.
Moreover the total evolved is similar for each test run suggesting
there is very limited if any residual detection from the previous
sampling. Table 3 shows the total production of the monitored gases
over 1.5 hours and the first 15 minutes of a sample run. During the
first 15 minutes of sampling there is a spike in production
(discussed in detail below). Table 3 also shows the total
production of monitored compounds minus the average production from
the sealed empty chamber with synthetic air flow at a rate of 660
mL/min (e.g. the same conditions as per sample test).
[0130] FIGS. 1 and 2 show the results for all four dressings for
HONO and NO production respectively. Both these compounds show
similar traits, both show a rapid sharp peak in production almost
instantly upon the dressing being assembled and the chamber being
sealed. Likewise both compounds appear to drop reasonably rapidly
to a steady state of production just above the baseline. The NO
production appears to drop to this steady state more rapidly than
HONO production; at approximately 1500 seconds and 3000 seconds
respectively. There also appears to be a reasonable overlap of the
traces at later stages of testing suggesting reasonably consistent
production between dressings. However during the initial production
spike there are visible differences between the dressings.
Furthermore during the first portion of HONO production there is
very little noise when compared to NO; however over time the level
of noise in HONO production increases.
[0131] The results for NO.sub.2 are shown in FIG. 3, in this
instance the pattern of production is unlike the other compounds in
that there appears to be a slight dip below the baseline in the
initial phase of production. Following this initial phase the
levels to rise a steady state; while FIG. 3 may appear very `noisy`
is should be noted the scale is considerably smaller than that of
FIGS. 1 and 2. FIGS. 4-7 show the results per dressing allowing a
visual representation of how each compound relates to one another,
in this context the NO.sub.2 production is significantly lower.
[0132] FIGS. 4-7 show a plot of NO, HONO and NO.sub.2 production at
ca. 299K for each dressing converted into nmol/mL. This was
calculated using the equation Xppm=0.0408*X nmol/mL. Total
quantification for each compound (in nmol) is shown in table 5. As
noted earlier all dressings show consistent patterns in the
production of all three compounds of interest. It is worth noting
that across the whole testing time frame the production of NO
appears to be significantly greater than that of the other
compounds. This is highlighted by the yield calculations of table
2. It is known that at the lower levels of detection (e.g. sub
parts per million) NO detection becomes difficult on SIFT-MS due to
interference from the NO+ reagent ion. This is mitigated by the
proportionally large production of NO from the dressing.
[0133] As mentioned all four repeats discussed thus far have been
with airflow over the dressing of 660 mL/min. In the initial phase
of testing a run was done with a significantly lower flow of the
same synthetic air at approximately 50 mL/min (FIG. 8). At the
lower flow the patterns in production are broadly similar to that
of the higher flow rate in so far as there is an almost instant
spike upon sealing the chamber followed by a drop in production to
a steady state (with the exception of NO.sub.2). However in this
instance the steady state of production occurs at a significantly
higher level than at the higher flow rate. This is most likely
attributed to the possibility that production occurs at a more
rapid rate than the air can leave the chamber and thus the gases
are collected and in effect concentrated. Alternatively the higher
flow rate may be providing a dilution effect which would also
result in this pattern. Following this method of testing the
chamber takes significantly longer to return to an appropriate
baseline level than after higher flow rate testing. This therefore
provides us with evidence that for this particular permutation of
testing the higher 660 mL/min flow rate is more appropriate.
[0134] In order to achieve something of an analogue to an in vivo
test the dressing was also analysed face down stuck over the sample
inlet tube; the gathered results can be seen in FIG. 9. For this
experiment no air flow was used and the chamber lid was removed,
thus eliminating any concentration effects from the chamber. The
HONO trace is not included for the full dressing analysis as this
was part of another trace and would make for an inappropriate
comparison. Once again we see a familiar pattern in the production
of each compound. The NO peak while monitoring facedown is very
sharp, it is also notable that the difference between the peak
production for the full and quarter dressing is not as large as
anticipated; approximately 280 to 260 ppm respectively. The full
dressings steady state is significantly higher (125 ppm full
dressing 40 ppm quarter dressing), though this this is not as big
as expected. If a quarter dressing on average produces 40 ppm one
might expect the whole dressing to produce 160 ppm (4 times the
amount), we find this does not occur and thus hypothesis that there
may be a relationship between the edges surface area and NO
production. HONO production during the steady state for the full
dressing was approximately 100 ppm compared to approximately 25 ppm
for the quarter dressing; these proportions are what one would
expect from a linear relationship between surface area and HONO
production.
[0135] Conclusion
[0136] The nitric oxide producing dressing has been analysed for
production of NO, NO.sub.2 and HONO under a number of different
permutations. The proportions of the compounds produced remained
very similar: NO.sub.2 production is by far the least abundant
regardless of methodology. HONO is produced in significant
quantities and appears to have an inverse relationship with NO;
thus it is important when considering the chemical processes taking
place. As expected NO production is by far the most consistent and
abundant compound (of those monitored).
[0137] The finding that high levels of NO and very low levels of
NO.sub.2 are produced is surprising, since until now it was assumed
that acidification of nitrite would give rise to equimolar ratios
of NO and NO.sub.2.
EXAMPLE 2
Production of Dressing System Using Hydrogel Compositions
[0138] Primary Layer: Wound Contact Mesh (Containing 1M Sodium
Nitrite)
[0139] The Mesh is a polypropylene mesh (RKW-Group), imbibed with
1M Sodium Nitrite solution, from Sodium Nitrite Extra Pure ph Eur,
USP Merck and deionised water.
[0140] Description of Manufacturing Process
[0141] Sodium nitrite is weighed into a suitably sized vessel and
then transferred carefully into a known volume of deionised water,
which is then stirred until dissolution is complete to make a
solution of appropriate concentration. In this embodiment the
sodium nitrite solution is dispensed onto the mesh and then is
placed into each petri dish for a minimum time to imbibe the mesh
with the sodium nitrite solution. The finished products are
sterilised by irradiation.
[0142] Secondary Layer: Hydrogel Top Layer
[0143] The hydrogel chosen for this study has high capability for
absorption and facilitates a moist wound-healing environment. The
hydrogel comprises a cross-linked anionic copolymer, circa 30%
water and circa 30% glycerol. It has an outer polyurethane film
that provides a bacterial barrier and aesthetically pleasing outer
surface to the dressing. The gels have an acidic surface pH circa
2-5 arising from the presence of some sulfonic acid groups. These
groups provide the acidity for the conversion of Sodium Nitrite to
Nitric Oxide. As the sulfonic acid groups are covalently bound to
the hydrogel network they are not released into the wound.
[0144] Description of Manufacturing Process
[0145] The hydrogel is manufactured from the list of ingredients
set out below. The process of manufacture is as according to
patents EP1100555B1 and EP110556B1, which are incorporated by
reference in their entirety herein.
[0146] The ingredients are dispensed into a suitable mixing vessel
(dispensing is controlled by weight) and stirred overnight. Once
mixed, a portion of the liquid solution is dispensed onto a moving
substrate (clear polyurethane film, Inspire 2304) at the required
coat weight. Then a mesh made of polypropylene (RKW 20 g/m.sup.2)
is laid onto the top of the liquid formulation, which is then
exposed to UV light and cured. A second layer is coated on top of
the first at the required coat weight and exposed to UV light, thus
making a "sandwich" with the mesh in the middle.
[0147] The hydrogel is cut to the required size and pouched, sealed
and sterilised. The finished products are sterilised by gamma
irradiation.
[0148] The components of the hydrogels are:
[0149] Monomer, Sodium AMPS 2405A (58% solution in water)
(Lubrizol)
[0150] Monomer, 2-acrylamido-2-methylpropane sulfonic acid
(Sigma-Aldrich)(AMPS Acid)
[0151] Monomer, Acrylic Acid (BASF)
[0152] Glycerine BP, EP (H. Fosters)
[0153] Darocur 1173, 2-hydroxy-2-methylpropiophenone (BASF)
(D1173)
[0154] SR 344, poly (ethylene glycol) diacrylate (Sartomer) (PEG
diacylate)
[0155] Mesh, Carded non-woven 20 gsm (RKW-Group)
[0156] Inspire 2304, polyurethane film (Coveris)
[0157] 70 micron, low density polyethylene, siliconised
(Adcoat)
[0158] `NeoCarta,` peelable laminate (Safta)
[0159] The components of the nitrite layer are:
[0160] Mesh, Carded non-woven 20 gsm (RKW-Group)
[0161] `NeoCarta,` peelable laminate (Safta)
[0162] Sodium Nitrite, extra pure, Ph Eur, USP (Merck)
[0163] De-ionised water (First Water Ltd)
[0164] Example Hydrogel Compositions
TABLE-US-00006 TABLE 6 example hydrogel compositions. Sample 1
Sample 2 Sample 3 Sample 4 Component Parts (g) Parts (g) Parts
Parts (g) Na AMPS 2405A 66 67 67 67 AMPS Acid 1.03 0.4 0.05 --
Acrylic Acid -- -- -- 2 Glycerol 30 30 30 30 D1173 and PEG 0.12
0.12 0.12 0.12 diacrylate (in a 4:20 w/w ratio)
EXAMPLE 3
Production of a Wound Dressing
[0165] A wound dressing of the invention can be made by placing the
first layer, made by imbibing a 5 cm.times.5 cm "nitrite mesh" of
Example 2 with 0.05 to 1 g of 0.01M to 2M sodium nitrite,(specific
example 0.2 g of 1M sodium nitrite) onto a wound and covering the
first layer with a second layer comprising a source of hydrogen
ions. The second layer may be for example Medihoney HCS(11
cm.times.11 cm)(Derma Sciences), AQUACEL.RTM.(10 cm.times.10
cm)(ConvaTec), AQUACEL.RTM. Ag (10 cm.times.10 cm)(ConvaTec),
AQUACEL.RTM. Ag Foam (10 cm.times.10 cm(ConvaTec)), AQUACEL.RTM.
Foam (10 cm.times.10 cm)(ConvaTec), AQUACEL.RTM. EXTRA (10
cm.times.10 cm)(ConvaTec), Granuflex (10 cm.times.10
cm)(ConvaTec).
EXAMPLE 4
Selected Ion Flow Tube Mass Spectrometry Analysis of Alternative
Nitric Oxide Generating Dressing Systems
[0166] The production of NO, NO.sub.2 and HNO.sub.2 by dressings
based on either Medihoney or AQUACEL was tested using Selected Ion
Flow Tube Mass Spectrometry (SIFT-MS).
[0167] SIFT-MS was carried out as described with respect to Example
1, using a flow rate of 660 ml/min.
[0168] AQUACEL is carboxymethyl cellulose based fibre, in which
carboxylic acid groups are copolymerised into the polymer network.
In this experiment, a dry AQUACEL (10 cm.times.10 cm) (ConVatec)
dressing was cut in half to form a 5 cm.times.5 cm square and
placed into the sample chamber. A 2.5 cm.times.2.5 cm (0.0145 mg)
of polypropylene non-woven mesh imbibed with 34.5 mg of a 1M sodium
nitrite solution was placed on top of the Aquacel sample and the
sample chamber then closed and SIFT-MS data collected. FIG. 10
shows the output from SIFT-MS for this experiment. As can be seen,
the production of NO is favourable compared to NO.sub.2 and
HNO.sub.2 production.
[0169] Medihoney HCS is a gel dressing comprising greater than 50%
Manuka honey. In the following experiment Medihoney HCS was used as
the sole source of hydrogen ions. A Medihoney HCS (10 cm.times.10
cm) (Derma Sciences) dressing was cut in half to form a 5
cm.times.5 cm square and placed into the sample chamber. A 2.5
cm.times.2.5 cm (0.0145 mg) of polypropylene non-woven mesh imbibed
with 34.5 mg of a 1M sodium nitrite solution was placed on top of
the Medihoney sample and the sample chamber then closed and SIFT-MS
data collected. FIG. 11 shows the output from SIFT-MS for this
experiment. As can be seen, the production of NO is favourable
compared to NO.sub.2 and HNO.sub.2 production.
* * * * *
References