U.S. patent application number 10/543799 was filed with the patent office on 2006-06-22 for dermal drug delivery system.
Invention is credited to Marc Barry Brown, Gary Peter Martin.
Application Number | 20060130266 10/543799 |
Document ID | / |
Family ID | 36593861 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060130266 |
Kind Code |
A1 |
Brown; Marc Barry ; et
al. |
June 22, 2006 |
Dermal drug delivery system
Abstract
A device for brushing the skin prior to applying a topical
preparation of a drug enhances the permeability of the stratum
corneum to the drug.
Inventors: |
Brown; Marc Barry; (Watford,
GB) ; Martin; Gary Peter; (Lewes, GB) |
Correspondence
Address: |
GREENLEE WINNER AND SULLIVAN P C
4875 PEARL EAST CIRCLE
SUITE 200
BOULDER
CO
80301
US
|
Family ID: |
36593861 |
Appl. No.: |
10/543799 |
Filed: |
December 16, 2004 |
PCT Filed: |
December 16, 2004 |
PCT NO: |
PCT/GB04/05274 |
371 Date: |
January 24, 2006 |
Current U.S.
Class: |
15/329 |
Current CPC
Class: |
A61H 7/002 20130101;
A61B 2017/00761 20130101; A61B 17/205 20130101; A61B 17/20
20130101; A61B 2017/320012 20130101 |
Class at
Publication: |
015/329 |
International
Class: |
A47L 5/00 20060101
A47L005/00 |
Claims
1. A mechanised brushing device, wherein the mechanism of the
device is adapted to rotate a brush in contact with the skin of a
patient, the device having abutment means for contact with the
skin, the brush being movably located in relation to the abutment
means to allow it to be introduced to the skin, travel of the brush
being limited in relation to the abutment means such that pressure
on the brush to contact the skin is limited to a predefined
range.
2. A device according to claim 1, further comprising pressure
limiting means.
3. A device according to claim 1, adapted to provide a contact
pressure of the brush of between about 200 and about 1500 N
m.sup.-2 on the skin.
4. A device according to claim 3, wherein the pressure is between
about 200 and about 1000 Nm.sup.-2,
5. A device according to claim 4, wherein the pressure is about
equal to, or greater than, 300 N m.sup.-2.
6. A device according to claim 4, wherein the pressure is between
about 300 and about 600 N m.sup.-2.
7. A device according to claim 1, comprising a timing mechanism to
limit the duration of the brushing.
8. A device according to claim 1, adapted to provide brushing for
between about 10 seconds and 5 minutes.
9. A device according to claim 8, adapted to provide brushing for
between about 10 seconds and about two minutes.
10. A device according to claim 8, adapted to provide brushing for
between about 20 seconds and one minute.
11. A device according to claim 8, adapted to provide brushing for
between about 30 seconds and about 50 seconds.
12. A device according to claim 1, wherein the brush is
substantially Robertson grade 8, and is adapted to provide brushing
for between about 15 seconds to about 40 seconds.
13. A device according to claim 1, adapted to provide an
oscillatory brushing motion.
14. A device according to claim 13, wherein the oscillatory motion
is essentially circular.
15. A device according to claim 13, wherein the rate of said motion
is between 30 and 300 rpm.
16. A device according to claim 15, wherein the rate of said motion
is between 50 and 200 rpm.
17. A device according to claim 15, wherein the rate of said motion
is between 60 and 120 rpm.
18. A device according to claim 1, wherein that part of the brush
for contact with the skin consists essentially of bristles, and
wherein said bristles have a Robertson number of from about 6 to
about 11.
19. A device according to claim 18, wherein the Robertson number is
from about 7 to about 10.
20. A device according to claim 18, wherein the Robertson number is
from about 8 to about 9.
21. A device according to claim 18, wherein the Robertson number is
about 8.
22. A device according to claim 1, wherein the cross-sectional area
of that part of the brush for contact with the skin is between
about 1 mm.sup.2 and about 10 cm.sup.2.
23. A device according to claim 22, wherein the cross-sectional
area is about 4 mm.sup.2 to about 5 cm.sup.2.
24. A device according to claim 22, wherein the cross-sectional
area is about 5 mm.sup.2 to about 2 cm.sup.2.
25. A method for the conditioning of skin to enhance transdermal
delivery of drug, the method comprising continuous brushing for a
period sufficient to reduce the barrier qualities of the stratum
corneum.
26. A method according to claim 25, comprising, substantially
immediately after brushing the area of skin to be treated, applying
said drug to the brushed area.
27. A method for the conditioning of skin to enhance transdermal
delivery of drug, the method comprising continuous brushing for a
period sufficient to reduce the barrier qualities of the stratum
corneum, wherein said brushing is provided by the mechanised
brushing device of claim 1.
28. A kit comprising the mechanised brushing device of claim 1 and
a drug wherein said drug is selected from the group consisting of:
crotamiton, doxepin hydrochloride, mesulphen, polidocanol,
amethocaine, amylocaine, benzocaine, bucricaine, butacaine
sulphate, butyl aminobenzoate picrate, cincocaine, dimethisoquin
hydrochloride, dyclocaine hydrochloride, ethyl chloride, lidocaine,
lignocaine, myrtecaine, oxethazaine, prilocaine, propanocaine
hydrochloride, tetracaine, antihistamines, antazoline,
chlorcyclizine hydrochloride, dimethindene maleate,
diphenhydramine, histapyrrodine, isothipendyl hydrochloride,
mepyramine, mepyramine maleate, tolpropamine hydrochloride,
tripelennamine hydrochloride, triprolidine hydrochloride,
corticosteroids, alclometasone dipropionate, beclomethasone
dipropionate, betamethasone valerate, clobetasol propionate,
clobetasone butyrate, desoximetasone, diflucortolone valerate,
fludroxycortide/flurandrenolone, fluocinolone acetonide,
hydrocortisone, hydrocortisone acetate, hydrocortisone butyrate,
calcipotriol, coal tar, dithranol, 5-fluouracil, ciclosporin,
fumeric acid, lonapalene, methotrexate, methoxsalen, salicylic
acid, tacalcitol, tacrolimus, pimecrolimus, tazarotene, azelaic
acid, benzoyl peroxide, amorolfine, benzoic acid, bifonazole,
bromochlorosalicylanilide, buclosamide, butenafine hydrochloride,
chlormidazole hydrochloride, chlorphenesin, ciclopirox olamine,
clotrimazole, croconazole hydrochloride, eberconazole, econazole
nitrate, fenticlor, fenticonazole nitrate, flutrimazole,
haloprogin, ketoconazole, mepartricin, miconazole nitrate,
naftifine hydrochloride, natamycin, neticonazole hydrochloride,
nystatin, omoconazole nitrate, oxiconazole nitrate, pyrrolnitrin,
sertaconazole nitrate, sodium propionate, sulbentine, sulconazole
nitrate, sulconazole nitrate, terbinafine, tioconazole, tolciclate,
tolnaftate, triacetin, undecenoates/undecanoic acid, 1-docosanol,
aciclovir, brivudine, edoxudine, ibacitabine, idoxuridine,
idoxuridine in dimethyl sulfoxide, imiquimod, penciclovir,
vidarabine, benzyl benzoate, carbaryl, malathion, permethrin,
phenothrin, cetrimide, collodion, magnesium sulphate, proflavine,
heparinoid, antiperspirants, aluminium chloride, glycopyrronium
bromide, and mixtures thereof.
29. A kit comprising the mechanised brushing device of claim 1 and
a drug wherein said drug is selected from the group consisting of
non-steroidal anti-inflammatories, actinic keratosis treatments,
and capsaicin.
30. A kit comprising the mechanised brushing device of claim 1 and
a drug wherein said drug is a hydrophilic drug.
31. A kit according to claim 30, said drug having a Log P of
.ltoreq.2.
32. A kit according to claim 30, said drug having a Log P of
.ltoreq.1.
33. A kit according to claim 30, said drug having a Log P of 0 or
below.
34. A kit comprising the mechanised brushing device of claim 1 and
a drug wherein said drug is selected from the group consisting of:
methotrexate, aciclovir, dactinomycin, oxytetracycline,
5-fluorouracil, ipatropium bomide, chlortetracycline, ceterizine,
carboplatin, aminophylline, ofloxacin, pravastatin sodium,
dichloromethotrexate, isoniaziad, theopylline, doxycyline,
metronidazole, procaine, 4-aminosalicyclic acid, baclofen,
triamcinolone, lidocaine/lignocaine, minoxidil, and combinations
thereof.
35. A kit comprising the mechanised brushing device of claim 1 and
a substance wherein said substance is a protein or peptide, nucleic
acid, or a related compound.
36. A kit according to claim 35, wherein said substance is capable
of stimulating an immune response when applied to the skin by a
device as defined in claim 1.
Description
[0001] The present invention relates to the delivery of drugs by
abrading the skin, and devices for use with such methods.
[0002] In order for therapeutic quantities of drug to penetrate the
skin, the barrier properties of the stratum corneum must be
overcome. The stratum corneum exhibits selective permeability and
allows only relatively lipophilic compounds with a molecular weight
below 400 Daltons to pass.
[0003] Methods of overcoming the barrier properties of the stratum
corneum may be divided into chemical, such as penetration enhancers
and supersaturated concentrations, and physical, such as
iontophoresis, skin electroporation, ultrasound and powder
needleless injection, methods. In the case of macromolecules
(>1000 Da) the use of physical methods has been shown to be
advantageous over chemical methods, and has led to a significant
increase in the number of topical/transdermal devices.
[0004] The mode of operation of these devices includes skin
disruption and microneedles/microblades. Gerstel (1976) was one of
the first to describe a drug delivery device for percutaneous
administration of drugs. The device consists of a drug reservoir
and a plurality of microneedles extending from the reservoir, for
penetrating the stratum corneum and epidermis to deliver the drug.
This device is the forerunner of many devices on the market today.
A recent commercialisation of this microneedle technology is the
Macroflux) microprojection array developed by Alza Corporation.
[0005] Most transdermal devices are currently based on patch
technology, and problems encountered include irritancy and poor
adhesion. Most patches only deliver about 10% of the total dose,
with the 90% of the drug remaining in the patch being
discarded.
[0006] Known abrasion devices are relatively expensive and can only
be operated by trained personnel, thereby limiting their ability to
be used by patients. Since it is also a painful surgical procedure,
anaesthesia is administered beforehand.
[0007] WO 01/89622 describes the use of an applicator with an
abrading surface on which the drug is coated.
[0008] We have now, surprisingly, found that the properties of the
stratum corneum can be substantially altered by a short period of
brushing, such that therapeutically effective amounts of drug can
pass thereacross.
[0009] Thus, in a first aspect, the present invention provides a
method for the conditioning of skin to enhance transdermal delivery
of drug, the method comprising continuous brushing for a period
sufficient to reduce, or perturb, the barrier qualities of the
stratum corneum.
[0010] In this respect, brushing affects the stratum corneum in
such a manner as to facilitate, normally, and preferably
temporarily, passage of a drug across it, by physically disrupting
the barrier thereby to reduce the resistance to the drug's
passage.
[0011] By "barrier qualities" is meant those properties of the
stratum corneum that inhibit the passage of drug. Reducing the
barrier qualities is also referred to herein as "enhancing
permeability" and other related terms.
[0012] By "transdermal" is meant delivery of drug across the
stratum corneum. In general, drugs delivered by such a route are
intended for local conditions of the skin, and are not usually
intended for systemic delivery. Thus, the drug will cross the
stratum corneum where, normally, it will then reach the required
site of action.
[0013] Any drug may be employed in the present invention, the term
"drug" here relating to any pharmaceutically active substance
capable of delivery across the stratum corneum in association with
the method of the present invention. Suitable examples of drugs are
given below.
[0014] The "continuous brushing" may be interrupted, if desired,
but it is intended that the brushing continue for a generally
consistent period ranging between about 10 seconds and 5 minutes,
although longer or shorter periods may be employed, depending on
the results to be achieved and the nature of the drug, as well as
other factors, such as pressure applied to the brush.
[0015] Thus, by "continuous" is meant that, between the start and
finish of the brushing process, the brushing should take place for
greater than 50% of the time, preferably greater than 80%, and is,
most preferably, substantially uninterrupted.
[0016] The nature of the brushing may be a simple backward and
forwards action, but is preferably oscillatory, and is particularly
preferably circular or rotatory. Not only is a circular brushing
motion easy to arrange and employ, but it has also been found that
the circular motion results in the greatest enhancement of the
permeability of the stratum corneum.
[0017] Without being limited by theory, it is believed that the
continuous brushing motion, especially when circular, not only
serves to stretch the skin slightly, but also serves to warm the
surface of the skin, both of these actions serving to enhance
penetration of drug.
[0018] What is particularly surprising is that this circular
brushing is able to increase, temporarily, the permeability of the
stratum corneum to such an extent that it is even greater than such
treatments as tape stripping, a process which is only generally
applicable to isolated skin and which substantially destroys the
integrity thereof. By contrast, the brushing of the present
invention only has a temporary effect on permeability but, whilst
the effect is achieved, the permeability is raised
substantially.
[0019] The drug may be applied in any suitable form. It is
generally preferred to apply the drug in the form of a solution,
gel, cream, emulsion, colloidal system, foam, mousse, suspension or
ointment, and the preparation may generally comprise further
ingredients, such as penetration enhancers and emollients.
[0020] Suitable drugs for use in accordance with the present
invention include, but are not limited to, those in the following
Table, either individually or in combination: TABLE-US-00001 Type
Of Drug Local antipruritics Crotamiton Doxepin hydrochloride
Mesulphen Polidocanol Local anaesthetics Amethocaine (Hydrochloride
in solutions or creams, base in gels or ointments) Amylocaine
(Hydrochloride) Benzocaine Bucricaine (hydrochloride) Butacaine
Sulphate Butyl Aminobenzoate Picrate Cincocaine (base,
hydrochloride or benzoate) Dimethisoquin Hydrochloride Dyclocaine
Hydrochloride Ethyl Chloride Lidocaine Lignocaine Myrtecaine
Oxethazaine (Oxetacaine) Prilocaine Propanocaine Hydrochloride
Tetracaine Antihistamines Antazoline Chlorcyclizine Hydrochloride
Dimethindene Maleate Diphenhydramine Histapyrrodine Isothipendyl
Hydrochloride Mepyramine Mepyramine Maleate Tolpropamine
Hydrochloride Tripelennamine Hydrochloride Triprolidine
Hydrochloride Corticosteroids Alclometasone dipropionate
Beclomethasone dipropionate Betamethasone valerate Clobetasol
propionate Clobetasone butyrate Desoximetasone Diflucortolone
valerate Fludroxycortide/Flurandrenolone Fluocinolone acetonide
Hydrocortisone Hydrocortisone acetate Hydrocortisone butyrate
Topical preparations for Calcipotriol psoriasis Coal tar Dithranol
5-Fluouracil Ciclosporin Fumeric acid Lonapalene Methotrexate
Methoxsalen Salicylic acid Tacalcito Tacrolimus Pimecrolimus
Tazarotene Topical preparations for acne Azelaic acid Benzoyl
peroxide Dithiosalicylic acid Motretinide Resorcinol Topical
antibacterials for acne Clindamycin Erythromycin `Dermatological
drugs` Becaplermin (Diabetic skin ulcers) Bentoquatum (prevents
allergic contact dermatitis caused by poison ivy) Gamolenic acid
Glycolic acid (Photodamaged skin) Hydroquinone/Mequinol
(Depigmenting agents) Ichthammol Keluamid (seborrhoeic dermatitis)
Lithium succinate Monobenzone (vitiligo) Polyphloroglucinol
Phosphate (Treatment of wounds and pruritic skin disorders) Sodium
pidolate (humectant, applied as cream/lotion for dry skin
disorders) Sulphur (mild antifungal/antiseptic) Sulphurated Lime
(For acne, scabies, seborrhoeic dermatitus) Sulphurated Potash
(Acne) Minoxidil (hair growth) Topical retinoids and related
Adapalene preparations for acne Isotretinoin Polyprenoic acid
Tretinoin Other topical preparations Nicotinamide for acne Topical
antibacterials Amphomycin Bacitracin/Bacitracin Zinc Bekanamycin
Sulphate Chloramphenicol Chlorquinaldol Chlortetracycline
Framycetin sulphate Fusidic Acid Halquinol Mupirocin Mupirocin
Neomycin sulphate Polymyxins (Polymyxin B Sulphate) Silver
sulphadiazine (sulfadiazine) Sulphanilamide Sulphasomidine
Sulphathiazole (sulfathiazole) Sodium Topical antifungals Benzoyl
peroxide Amorolfine Benzoic acid Bifonazole
Bromochlorosalicylanilide Buclosamide Butenafine Hydrochloride
Chlormidazole Hydrochloride Chlorphenesin Ciclopirox Olamine
Clotrimazole Croconazole Hydrochloride Eberconazole Econazole
nitrate Fenticlor Fenticonazole Nitrate Flutrimazole Haloprogin
Ketoconazole Mepartricin Miconazole nitrate Naftifine Hydrochloride
Natamycin Neticonazole Hydrochloride Nystatin Omoconazole Nitrate
Oxiconazole Nitrate Pyrrolnitrin Sertaconazole Nitrate Sodium
Propionate Sulbentine Sulconazole nitrate Sulconazole Nitrate
Terbinafine Tioconazole Tolciclate Tolnaftate Triacetin
Undecenoates/Undecanoic Acid Antiviral preparations 1-Docosanol
Aciclovir Brivudine Edoxudine Ibacitabine Idoxuridine Idoxuridine
in dimethyl sulfoxide Imiquimod Penciclovir Vidarabine
Parasiticidal preparations Benzyl benzoate Carbaryl Malathion
Permethrin Phenothrin Preparations for minor cuts Cetrimide and
abrasions Collodion Magnesium sulphate Proflavine Topical
circulatory preparations Heparinoid Antiperspirants Aluminium
chloride Glycopyrronium bromide
[0021] Other suitable drugs include the non-steroidal
anti-inflammatories (NSAIDs), actinic keratosis treatments, and
capsaicin.
[0022] The approach of the present invention may also be employed
in the delivery of protein and peptide substances, and related
compounds, such as peptidomimetics, and is of especial use in
immunisation programmes, whether for primary or booster shots, and
may be useful in BCG, for example. The invention further extends to
the delivery of nucleic acids and their related compounds and
derivatives. In the present context, a derivative or related
compound is one that has been modified from the original, or
prepared independently from the original, and which is used to
emulate or to provide an affect associated with the original. A
mimetic may simply comprise protecting groups, for example, or the
backbone may be modified to inhibit or block digestion of the
molecule.
[0023] In particular, it has been found that the present invention
is especially suited for the delivery of hydrophilic drugs. The
invention demonstrably increases the delivery rate of hydrophobic
drugs, also, but has an especially surprising effect with drugs
having a Log P of .ltoreq.2, and is even more pronounced and
beneficial with drugs having a Log P of .ltoreq.1, and especially
with drugs having a Log P of 0 or below. For example, caffeine can
be delivered at substantially increased rates using the present
invention, and has a Log P of -0.07, as shown in Table 2,
below.
[0024] Particularly preferred drugs for delivery using the present
invention are selected from; methotrexate, aciclovir, dactinomycin,
oxytetracycline, 5-fluorouracil, ipatropium bomide,
chlortetracycline, ceterizine, carboplatin, aminophylline,
ofloxacin, pravastatin sodium, dichloromethotrexate, isoniaziad,
theopylline, doxycyline, metronidazole, procaine, 4-aminosalicyclic
acid, baclofen, triamcinolone, lidocaine/lignocaine, minoxidil, or
combinations thereof.
[0025] The preparation of drug may be applied before, during, or
after brushing the skin, but the best effects are generally
observed by brushing the area of skin to be treated and then,
substantially immediately thereafter, applying the drug to the
brushed area While it is not essential to apply the drug
immediately after brushing, it will be appreciated that any
substantial delay will permit the skin to recover, so that the
enhanced permeability will be reduced, the longer the delay.
[0026] The nature of the brush is not critical to the present
invention. However, it is preferred that the bristles making up the
brush are presented in a substantially planar fashion to the skin,
although there may be some advantage to having slightly longer
bristles in the centre of the brush.
[0027] Where the bristles are presented in a substantially planar
fashion to the skin, then the area of skin over which the brush
moves will be generally equally treated, and there will be less
discrepancy of permeation enhancement with increasing-pressure.
[0028] The bristles forming the brush should be sufficiently
resilient as not to splay substantially under the pressures
suitable to put the invention into effect. These pressures will
generally range from about 20 g/cm.sup.2 to about 120 g/cm.sup.2,
and it will be appreciated that tougher, or more resilient,
bristles, are required with increasing pressure, in order to avoid
substantial bristle deformation. With frequency of use, it is
likely that a brush will start to deform, whereon it is generally
desirable to replace the brushing element. In any event, it is
frequently desirable to replace the brushing element between uses
where a device is intended for use on different patients. Where the
patient applies the treatment himself, then replacement may only be
necessary when the brush remains deformed after use.
[0029] It is generally preferred that the bristles not be too hard,
as this can lead to irritation and reddening of the skin which,
whilst it may be acceptable for an occasional treatment, is
undesirable where treatment is required on a more frequent basis,
such as daily, for example.
[0030] It has been found that the use of bristles having similar
qualities to those of hard brushes for use in domestic situations
for application to the person, such as nailbrushes, leads to very
substantially increased permeation qualities of the stratum
corneum, while not disrupting the structure of the stratum corneum
to any great extent, and that they can be used without causing any
substantial discomfort.
[0031] The stiffness of the bristle may also be referred to as the
Robertson number, and is commonly used in dentistry to define the
hardness of a brush. A Robertson #6 is generally considered to be
"soft", and is usually at the low end of the range for what is
suitable for use with the present invention, given that such
bristles deform under moderate pressure. To an extent, this can be
accommodated by packing the bristles tightly, but is not generally
as useful as using harder bristles.
[0032] In the accompanying Example, bristles of Robertson no. 8
provide excellent results, without having to cause distress to the
skin. It will be appreciated that exceedingly hard bristles, such
as wires, can be used, but these need to be employed with great
care in order not to damage the skin, so that a maximum of a
Robertson no. of 11 is preferred.
[0033] The most preferred Robertson numbers are from about 6 to
about 11, more preferably from about 7 to about 10, particularly
about 8 to about 9, especially about 8.
[0034] The duration of brushing is dependent on a number of
factors, including pressure on the brush, the hardness of the
bristles and the nature of the drug to be delivered. However, it
has generally been found that an appropriate length of time for
brushing skin is between about 10 seconds and about two minutes,
preferably between about 20 seconds and one minute, and more
preferably between about 30 seconds and about 50 seconds, with an
average of about 40 seconds generally providing a good guide. With
Robertson Grade 8 brushes, good efficacy is often observed at 15
seconds and above, and 25 seconds is often particularly
effective.
[0035] The pressure on the brush should preferably be not so great
as to cause substantial irritation, but requires to be sufficient
to have a permeabilising effect. As such, it has been found that a
weight of between 20 and 90 grams is generally effective, although,
at 90 grams and above, patient discomfort may be incurred.
[0036] In general, it has been established that a weight of about
between 30 grams and 80 grams is sufficient, with a weight of
between 40 grams and 60 grams being preferred. This weight is
generally in terms of the accompanying Example.
[0037] In terms of pressure, it is preferred to apply between about
20 gm/cm.sup.2 and about 100 gm/cm.sup.2, and more preferably
between about 40 gm/cm.sup.2 and about 80 gm/cm.sup.2.
[0038] The pressure applied to the brush may be any that is
effective to enhance delivery of the selected drug or drugs across
the stratum corneum. In terms of N m.sup.-2, particularly suitable
pressures are about 200 to about 1500 N m.sup.-2. Pressures of
greater than this may also be used, but generally require careful
control, short duration, and higher bristle strength, so are not
preferred. A more preferred range is about 200 to about 1000 N
m.sup.-2, with pressures of about equal to, or greater than, 300 N
m.sup.-2 being especially preferred. A most preferred range is
about 300 to about 600 N m.sup.-2.
[0039] The area of the end of the brush for contact with the skin
may be as small or as large as desired. For delivery of potent
drugs, for example, it may be desired to apply the formulation in a
diffuse fashion to a larger area, such as up to 500 cm.sup.2, in
which case it may be desirable to move the brush over the skin to
cover the whole of the target area, where the brush cross-section
is smaller than the target area. It may also be desired to target a
small area, or simply desired only to apply to a small area, to
minimise any possible pain, so that an area of about 1 mm.sup.2 may
be employed, for example. Smaller areas than this may provide
problems in finding bristles thin enough and strong enough to with
stand the pressure while abrading the skin without causing damage.
A small rotating brash with short bristles will often suffice,
under such conditions. In general, an area of skin in the
approximate region of 1 cm.sup.2 will often be the skilled
physician's area of choice.
[0040] Thus, an area of the end of the brush of between about 1
mm.sup.2 and about 10 cm.sup.2 is preferred, with a range of about
4 mm.sup.2 to about 5 cm.sup.2 being more preferred, and a range of
about 5 mm.sup.2 to about 2 cm.sup.2 generally being sufficient for
most applications.
[0041] The rate of oscillation, or rotation, of the brushes of the
invention may be any that serves, in combination with other
parameters, such as stiffness and cross-sectional area, to
sufficiently perturb the skin to enhance passage of drug. In the
accompanying Example, a rate of rotation of 80 revolutions per
minute (rpm) was found to be effective. Rates down to 30 rpm may be
employed, but will generally require stiffer bristles and greater
pressure to account for diminished interaction, while rates of
greater than 300 are increasingly associated with the risk of
damage to the skin by treatment that is too harsh. Thus, rates of
between 30 and 300 rpm are generally preferred, with rates of 50 to
200 rpm being more preferred, and rates of 60 to 120 rpm generally
being most preferred.
[0042] The present invention also extends to brushing devices for
the skin adapted to enhance the permeability of the stratum
corneum.
[0043] In one embodiment, the invention provides a mechanised
brushing device, wherein the mechanism of the device is adapted to
rotate a brush in contact with the skin of a patient, the device
having abutment means for contact with the skin, the brush being
movably located in relation to" the abutment means to allow it to
be introduced to the skin, travel of the brush being limited in
relation to the abutment means such that pressure on the brush to
contact the skin is limited to a predefined range.
[0044] Such a device may be adapted to dispense drug during, or
preferably after, brushing.
[0045] It will be appreciated that the term "mechanised" is used
herein to indicate that the brush is not, directly, manually
powered, but may be powered by any suitable means, such as
clockwork, solar-powered, battery-powered motor, electrically
powered, or spring-loaded, for example.
[0046] The brush will generally comprise a series of bristles which
may be individually mounted, or mounted in clusters, and which may
be made of any suitable material. It is preferred that the material
be resilient or flexible, in order not excessively to abrade the
skin. As a whole, the bristles should be sufficiently resilient to
be load-bearing, in that effective pressures may be applied through
them without substantial deformation at the recommended operating
pressure for the brush. As the bristles will generally be
resilient, some deformation under operating pressure is to be
expected. The brush will begin to lose efficiency when parts of the
bristle adjacent the terminus of the bristle, rather than the
terminus itself, begin to impact the skin.
[0047] The material from which the bristles is made is not critical
to the invention, and many suitable bristle materials are well
known in the art. Natural fibres, such as animal bristle, may be
employed, but it is generally more convenient to employ synthetic
polymers, such as polyamides.
[0048] For example, a rotary battery powered brush may be spring
mounted in an open ended sleeve. Pressure on the housing causes the
brush to move through the sleeve and to protrude beyond the
opening, a tongue and groove arrangement preventing the brush
protruding too far. The opening in the sleeve abuts the skin such
that, when the brush is at full extension and the sleeve is in
contact with the skin, then a weight of say 40 g is applied through
the brush.
[0049] A simple timing mechanism may also be employed for example,
to limit the duration to 40 seconds, for example.
[0050] One embodiment of this invention compromises a supporting
body (rigid structure, preferably made of plastic) from which an
array/plurality of bristles project vertically. The device is
applied to the patient's skin, in a position such that the tip of
the bristles make contact with the stratum corneum. A pre-wound
spring is incorporated into the supporting body, which when
released by means of a control button (located on the supporting
body) will allow the rotation/movement of the bristles in a
clockwise or anticlockwise manner for a defined period of time. The
number of rotations can then be controlled by the energy stored in
the spring, and the manner in which the supporting body is moulded
can also control the pressure exerted on the skin. This allows the
degree of attrition/perturbation/stretching of the stratum corneum
to be performed in a reproducible manner. Another embodiment of
this invention includes a system which will not only reduce the
barrier nature of the stratum corneum but also contain a
formulation which would be released at the same time.
[0051] In an alternative embodiment, a rotatably mounted brush is
located in an extensible fashion in a body, with electrically
powered motor means being provided to rotate the brush. A battery
may suitably provide the electrical power. Actuation of the motor
serves to engage the brush, and this may be combined, such that
extending the brush from the body actuates the motor. Preferably, a
timer device cooperates with the motor, such that the motor
switches off after a predetermined interval. The brush may then
automatically retract, or may be manually or otherwise
retracted.
[0052] The advantages offered by this system include the fact that
it not only abrades the skin but also stretches it temporarily
during treatment. This latter technique has been reported to
enhance skin permeation (Cormier et al, 2001).
[0053] Using the rotating brush method achieves the purpose of
reducing the barrier nature of skin with little or no pain,
compared to existing abrasion methods.
[0054] The ability of the device to enhance in vitro skin
permeability was investigated using the finite and infinite dose
technique. Butyl paraben, methyl paraben and caffeine were used as
model penetrants due to their similarity in molecular weight but
differences in lipophilicity. Changes in the structural properties
of the membrane were also probed, using scanning and transmission
electron microscopy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0055] FIG. 1a shows the effect of rotating brush A on skin
Permeation profile of CF at various pressures and durations;
[0056] FIG. 1b shows the effect of rotating device brush A on skin
Permeation profile of BP at various pressures and durations;
[0057] FIG. 1c shows the effect of rotating device brush A on skin
Permeation profile of MP at various pressures and durations;
[0058] FIG. 2a shows the effect of rotating device brush A and B on
skin permeation of CF;
[0059] FIG. 2b shows the effect of rotating device brush A and B on
skin permeation of MP;
[0060] FIG. 2c shows the effect of rotating device brush A and B on
skin permeation of BP;
[0061] FIG. 3 shows the results of a pseudo-finite dose study
comparing the effect of a device of the invention using brush B
with other established modes of skin permeation enhancement;
[0062] FIG. 4 shows the effect of treatment time on the skin
permeation profile of acyclovir using brush B;
[0063] FIG. 5 compares the effect of device treatment duration and
iontophoretic treatment on skin permeation of radiolabelled
.sup.3H-labelled acyclovir after 60 min.; and
[0064] FIG. 6 compares the effect of a device of the invention,
using brush B with other enhancement strategies on the skin
permeation of Ang II.
[0065] The present invention will now be illustrated by the
following non-limiting, Example.
EXAMPLE
[0066] A systematic investigation involving permeants of differing
lipophilicity and molecular weight was performed to evaluate
devices of the invention in enhancing skin permeation of permeants
with differing physicochemical properties.
Materials
[0067] The materials used in this Example were as listed in Table
1, below. TABLE-US-00002 TABLE 1 Materials used Materials and
Equipment Supplier Methyl paraben (MP) Sigma Chemical Co., Dorset,
UK Butyl paraben (BP) Caffeine anhydrous (CF) Triethylamine
Angiotensin (Ang) II .sup.3H-Acyclovir (ACV) Orthophosphoric acid
BDH Laboratory Supplies, Potassium dihydrogen Loughborough, UK
orthophosphate Methanol (HPLC grade) Rathburn Chemicals Ltd.,
Wakeburn, Acetonitrile (HPLC grade) Scotland Ethanol absolute (HPLC
grade) Phosphate Buffered Saline Oxoid Ltd, Basingstoke, England
(PBS) Deionised water (Elgstat Elga Ltd., High Wycombe, UK option
3A) Zovirax (5% Acyclovir cream) AAH supplies Enzyme immunoassay
kit Peninsula Laboratories Inc., California, USA Liquid
scintillation cocktail fluid Beckman Instruments Inc. California,
USA Brush A: Soft bristles Superdrug stores Plc, London, UK
(Robertson Grade 6, brush head of electric toothbrush) Brush B:
Hard bristles L. Cornelissen & Son Ltd, London, UK (Robertson
grade 8, hog hair bristles) Motor (Type KQPS 22) Citenco Ltd,
Borehamwood, Herts., UK
[0068] Brush Details [0069] Brush A [0070] Internally manufactured
[0071] Oscillatory brush, Robertson (6) pure bristles [0072]
Surface area of brush: 1.01 cm.sup.2 [0073] Brush B [0074] Source:
L. Comelissen & Son Ltd (London, UK) [0075] Brand name:
Robertson (8) pure bristles [0076] Surface area of brush: 1.61
cm.sup.2
[0077] A summary of the properties of the model penetrants is given
in Table 2, below, and a comparative description appears below.
TABLE-US-00003 TABLE 2 Physico-chemical properties of the model
penetrants Penetrant Molecular Weight (Da) Log P (o/w) Butyl
paraben (BP) 194.23 3.57 Methyl paraben (MP) 152.15 1.96 Caffeine
(CF) 194.19 -0.07 Acyclovir (ACV) 225.21 -1.56 Angiotensin (Ang) II
1046 -- BP, MP and CF have similar molecular weights but differ in
lipophilicity, thereby allowing the effect of the permeation
enhancement method of the invention lipophilicity to be studied.
ACV is an antiviral used in treating virus infections of the skin
and mucosa. It is poorly absorbed across the skin due to its
hydrophilic nature, hence reducing its therapeutic efficacy. ACV is
marketed as a cream and licensed to be used topically for the
treatment of cold sores, however, due to its retarded diffusion
across the skin, it is recommended to be applied five times daily.
Its dermato-pharmacological profile therefore # makes it a useful
model drug for testing the efficiency of the permeation method or
device of the invention. The use of ACV as a model marker in
investigating the potential of enhancement strategies such as
iontophoresis (Volpato at al., 1995, 1998; Stangi at al., 2004) and
ethosomes or ethanol based liposomes (Touitou at al., 2000) in
decreasing the skin barrier to improve ACV diffusion has been
reported. Ang II is a model hydrophilic, high molecular weight
peptide which would not ordinarily be absorbed across the skin by
conventional formulation approaches. Compared to the other model
penetrants described above, it is the least likely to permeate the
skin. Its use as a model marker to investigate the effect of
iontophoresis # and jet injection methods on the in vitro
permeability of large molecular weight solutes across animal skin
has also been reported (Clemessy at al., 1995; Sugibayashi at al.,
2000).
[0078] The effectiveness of the device of the invention in
increasing the permeability of the above markers was also compared
with some of the established and developmental methods of skin
permeation enhancement, such as tape stripping, chemical enhancers,
iontophoresis and delipidisation (removal of skin lipids).
Analytical Methods
HPLC analysis of MP, BP and CF
[0079] Chromatographic measurements were carried out using a Perkin
Elmer 200, LC Pump with Autosampler connected to a UW absorbance
Detector 759A (Applied Biosystems, Foster city, Calif., U.S.A). The
various HPLC methods employed for each penetrant were shown to be
fit for the purpose by ensuring reproducibility, repeatability,
linearity, and intermediate precision. Standard concentrations of
the model penetrants (0.1-20 .mu.g/ml) were prepared in PBS and
analysed. The chromatographic conditions for NT were as follows;
Hypersil.TM. 5.mu. BDS, C18 (150.times.4.6 mm, 5 .mu.m) column
(Phenomenex.RTM. Ltd, Cheshire, United Kingdom) with the mobile
phase comprising 35% acetonitrile: 65% phosphate buffer (0.05 M
KH.sub.2PO.sub.4 containing 1% triethylamine, then adjusted to pH
3.5 with orthophosphoric acid). BP chromatographic conditions
employed a Licrospher.TM., LispRP 18-5-1680, C18 (150.times.4.6 mm,
5 .mu.m) column (Hichrom.RTM. Ltd, Berkshire, England), with a
mobile phase of 50% acetonitrile: 50% phosphate buffer (0.02 M
KH.sub.2PO.sub.4 adjusted to pH 3.0 with orthophosphoric acid). CF
chromatographic conditions were as follows; Phenomenex.RTM.
Prodigy.TM. 5.mu. ODS 2, C18 (150.times.4.6 mm, 5 .mu.m), mobile
phase comprising 90% acetonitrile: 10% phosphate buffer (0.02 M
KH.sub.2PO.sub.4 adjusted to pH 3.0 with orthophosphoric acid).
Flow rate and injection volumes were set at 1 ml/min and 10 .mu.l
respectively for all penetrants. Wavelength of detection was set at
254 nm, 256 nm and 270 nm for MP, BP and CF respectively.
Analytical determination of CF was modified where necessary to
enhance its detection by increasing injection volume to 50 .mu.l
and using a wavelength of 215 nm.
Analytical Studies for ACV
[0080] The radiochemical purity of the .sup.3H-ACV to be used in
this study was determined by HPLC. Chromatographic measurements
were carried out using a Perkin Elmer, as described previously. ACV
chromatographic conditions were as follows; Phenomenex.RTM.
Prodigy.TM. 5.mu. ODS 2, C18 (150.times.4.6 mm, 5 .mu.m), mobile
phase comprising 90% acetonitrile: 10% phosphate buffer (0.02 M
KH.sub.2PO.sub.4 adjusted to pH 3.0 with orthophosphoric acid).
Flow rate, injection volumes and wavelength of detection were set
at 1 ml/min, 10 .mu.l and 250 nm respectively.
[0081] The purity of the .sup.3H-ACV was determined by accurately
spiking a 10 .mu.l aliquot of the radiolabelled drug into 1.0 ml of
PBS, which was then injected. The purity of the radioactivity was
determined by collecting sample fractions at 1 min time intervals
from time 0 to 30 min.
[0082] Zovirax.RTM. spiked with .sup.3H-ACV was used as the
formulation for the entire study. Briefly, 300 .mu.l of .sup.3H ACV
was placed into a 1.5 ml centrifuge tube and evaporated off, over a
stream of air. Approximately 1 g of Zovirax.RTM. was weighed into
the centrifuge tube and carefully mixed with a fine spatula to
achieve a homogenous mix. To test for homogeneity, 3 random samples
(top, middle and bottom) were taken and determined for
radioactivity via scintillation counting. This process was repeated
until the % coefficient of variation (CV) was below 2.5%.
Analytical Development Studies for Angiotensin II
[0083] Analysis of the peptide was carried out using an enzyme
immunoassay (EIA) as described in the EIA booklet. Briefly, a
competitive enzyme immunoassay which detects Ang II in biological
matrices was employed. The principle of the assay is based upon the
competition for antibody binding sites between biotinylated and
non-biotinylated peptides. The biotin group on the biotinylated
peptide is then conjugated to SA-HRP which in turn reacts with
another substrate (TUB) leading to the formation of colour. The
absorbance recorded from each well is a direct measure of the
extent of binding for each peptide with the antibody. Absorbance
was measured using a spectrophotometer. The method was validated by
calibrating the response at different concentrations of the peptide
(data not shown) and also the ability of the method to assess
different concentrations of the penetrant in the presence of any
matrices was investigated.
In vitro Skin Permeation Studies
Preparation of Human Epidermal Sheets
[0084] Human skin was obtained from cosmetic surgery with informed
consent. The epidermis was removed by the standard heat separation
method (Khigman and Christophers, 1963). Following removal of
subcutaneous fat, individual portions of skin were immersed in
water at 60.degree. C. for 45 seconds. The skin was then pinned,
dermis side down, on a cork board and the epidermis (comprising
stratum corneum and viable epidermis) gently removed from the under
lying dermis. The latter was discarded and the epidermal membrane
floated onto the surface of water and taken up onto a Whatman no. 1
filter paper. The resultant epidermal sheet were thoroughly dried
and stored flat in aluminum foil at -20.degree. C. until use.
Tape-Stripping Procedure
[0085] Tape-stripping was employed in order to partially remove the
upper layers of the skin where the barrier properties are known to
reside. Tape-stripped skin sections used were prepared by repeated
stripping skin with D-squame.RTM. adhesive disc. The disc was
gently placed on the skin after which a known weight was placed
into the adhesive disc skin composite for 20 s. The weight was then
lifted and the adhesive disc removed. This was then repeated eight
times. The permeability profile across the tape-stripped skin was
then investigated via Franz cell studies.
Skin Delipidisation Procedure
[0086] The objective here was to remove the intercellular lipids of
the SC in order to investigate the potential pathway employed by
the model markers in their bid to cross the skin barrier.
Delipidised skin was prepared by immersing skin sections in
chloroform and methanol (2:1) for. 40 min Rastogi and Singh,
2001a,b), after which the skin was removed, blotted dry with tissue
and dried via vacuum drier at 760 mm Hg, 25.degree. C., for 1 hr,
to remove any remaining organic solvent. The delipidised skin was
then used for Franz cell studies.
Chemical Enhancement Procedure (50% Ethanol in PBS)
[0087] The ability of ethanol to reduce the barrier property of the
SC has been well documented (Williams & Barry, 2004). This was
conducted by forming a saturated solution of each penetrant
containing 50% v/v ethanol (EtOH), which was allowed to stir
overnight. The resulting solution was then introduced into the
donor well the Franz cells.
Iontophoresis or Post-Iontophoresis (Pre-Treatment)
[0088] This is a well established physical method of enhancing skin
permeation, in vitro, which involves the use of electric current to
permeabilise skin and/or promote the migration of drug ions across
skin (Cullander, 1992; Guy et al., 2001; Kalia et al., 2004).
Anodal treatment was conducted by placing the anode electrode in
the donor compartment and the opposite electrode (cathode) in the
receptor compartment of the Franz cell. Cathodal iontophoresis was
conducted vice versa. The current treatment protocols employed were
either [0089] (a) iontophoresis: dose was administered
simultaneously with current or [0090] (b) post-iontophoresis: dose
applied immediately after skin exposure to current. [0091] A
current intensity of 0.40 mA was employed for a 10 min period
during both protocols. Novel Device (Rotatinig Brush) Procedure
[0092] The potential device parameters affecting permeation were
identified as follows: [0093] (a) speed of bristles/frequency of
movement; [0094] (b) pressure exerted on epidermal membrane
surface; [0095] (c) duration of treatment; and [0096] (d) nature of
bristle; hard or soft.
[0097] The mode of treatment was controlled as follows:
[0098] The piece of epidermal sheet with demarcated regions of
interest was 1a id on to a microscope slide which was then placed
onto a weighing balance.
[0099] The balance was supported by a jack (lift) sitting directly
under the device the cell was then tarred.
[0100] With the aid of the jack, the device was partially lowered
(by increasing the height of the jack using the control knob)
ensuring that the bristles did not touch the epidermal surface.
[0101] The device was then switched on, and the slide moved until a
position was found where the bristles are directly under the
demarcated region of the epidermal sheet.
[0102] The device was then switched off. The slide was then
attached firmly to the balance by means of scotch tape (tape
extends from non demarcated region of epidermal sheet to balance,
avoid contact between tape and demarcated region to ensure no
movement of the slide during treatment).
[0103] Once the slide was in a stationary position, the device was
switched on, ensuring that the speed dial was at the required
position. The device was gently lowered (by raising the jack as
described above) until the bristles touched the surface, the
reading on the balance then gave an indication of the weight
(pressure) exerted on the membrane surface.
[0104] The required pressure was then attained by using the control
knob of the jack to lower or increase the height of the balance.
The slide then remained stationary during the duration of
treatment. The pressure/weight exerted on the membrane during
treatment was then read directly from the balance.
[0105] After treatment the scotch tape was carefully removed. The
demarcated circular region was then cut off from the remaining
epidermal sheet by means of a cork borer, then placed in a Franz
cell.
[0106] An integrity check was also conducted after skin treatment
to ensure that the bristles did not create holes in the epidermal
layer. This was performed by inversion of the Franz cell to observe
whether the receptor fluid liquid was leaking through membrane.
Franz Cell Studies
Optimisation Studies using 3 Model Penetrants; Infinite Dose
Study
[0107] The study was conducted using human epidermal sheets (since
the barrier properties reside in the stratum corneum) to determine
the amount of the model marker penetrating the membrane over a 4 hr
period. Calibrated Franz cells of known area (.about.0.65 cm sq)
and volume (.about.2 ml) were used. The receptor chamber was filled
with PBS (pH 7.4) and stirred throughout the duration of the
experiment by a PTFE coated magnetic flea. The membrane was clamped
in between the donor cap and receptor chamber of the Franz cell
(stratum corneum facing upwards), was then treated with the two
types of bristles at different pressures and contact time, whilst
maintaining a constant device speed (Table 3, below).
TABLE-US-00004 TABLE 3 Device parameters used during optimisation
studies Speed (rpm) 80 Brush (bristle type) Soft (A) and hard (B)
Pressure applied on skin (Nm.sup.-2) 300-1200 Treatment duration
(s) 15-45
[0108] 250 .mu.l of saturated solution of the model penetrant in
PBS was then directly introduced into the donor chamber of the
cell. All experiments were conducted in a water bath at 37.degree.
C. In order to determine the enhancement effect of the rotating
brush, control experiments involving the use of non-treated
(intact), tape stripped, donor solutions of marker containing 50%
ethanol and delipidised epidermal membranes were also
performed.
Pseudofinite Dose-Studies (Acyclovir and CF)
[0109] Finite dose permeation experiments were performed using
similar conditions as described above. The Franz cell studies were
carried out without the use of a donor well, in order to allow for
the placement of the iontophoretic device over the epidermal
membrane. In addition, the epidermal membrane was mounted onto the
receptor well using cyanoacrylate adhesive and ensuring that there
was no contact between the adhesive and the effective surface area
available for drug permeation. After a drying time of 15 min, the
receptor well was then filled with the receptor fluid (PBS). The
effectiveness of the seal was confirmed if leakage of receptor
fluid from the region of contact between skin and adhesive was not
observed.
[0110] The skin was treated with the novel device using optimised
parameters obtained from the preceding section of this Example. A
formulation with a target dose of approximately 9.+-.1 mg/cm.sup.2
(ACV) and 20.+-.2 mg/cm.sup.2 (CF) was applied to the epidermal
membrane surface using a previously calibrated positive
displacement pipette. Selected control experiments were then
performed as described above (anodal and cathodal iontophoresis was
performed by simultaneous application of dose and current over a 10
min period for CF and ACV respectively). At certain time intervals
200 .mu.l of the receiver fluid was carefully withdrawn from the
receiver fluid (maximum duration of 4 h). Approximately 4 ml of
scintillation cocktail was then added and the ACV sample analysed
by scintillation counting, whereas the other penetrant was assayed
via the HPLC method already described.
Angiotensin II-Infinite Dose
[0111] A similar procedure described in the preceding optimisation
section was conducted for Ang II, whereby the diffusion of the
peptide across skin following brush treatment was compared against
all the treatment methods. A 250 .mu.l solution of Ang II in PBS (1
mg/ml) was then introduced into the donor well. The receptor
chamber was filled with EIA buffer, previously treated via
ultrasound to prevent the formation of air bubbles. Receptor fluid
was sampled after a 4 h and 24 h period and analysed via the EIA
method described.
Histological Studies
[0112] The effect of bristle perturbation on the epidermis was
assessed by scanning and transmission electron microscopy, where
the integrity of brush treated and untreated (control) samples were
compared. Brush treated and untreated (control) samples were fixed
in 2% formaldehyde/2.5% glutaraldehyde in 0.1M phosphate buffer pH
7.4 overnight. Scanning electron microscopy (SEM) was performed as
follows: A 5.times.5 mm square of skin was pinned to a thin piece
of cork in order to keep it flat during processing. Samples were
immersed 20 min in each of 30, 50, 70, 95, 100, 100, 100% v/v
acetone in water, then dried using liquid carbon dioxide in a
Polaron E3000 critical point drier. The samples were then removed
from the cork and mounted on 12.5 mm aluminum pin stubs using
double sided adhesive carbon pads. Samples were sputter coated with
approximately 20 nm of gold in a Polaron E5100 sputter coater and
examined and photographed using a Philip SEM501B scanning electron
microscope. For transmission electron microscopy (TEM), a 1.times.2
mm strip was cut from the fixed skin, then dehydrated by sequential
immersion in acetone at increasing concentrations and embedded in
spurr resin and polymerised for 48 hr at 60.degree. C. Ultra-thin
sections were cut on a Reichart Jung OMU4 ultra microtome using a
diamond knife and then taken up on 200 mesh hexagonal copper grids.
Sections were stained for 15 min in 1% w/w uranyl acetate in 50%
v/v ethanol in water followed by 5 minutes in Reynold's lead
citrate. These sections were examined and photographed using a JEOL
JEM100CX II transmission electron microscope.
Data Interpretation & Statistical Analysis
[0113] Since the SC is made up of dead cells no active transport
processes exist. Transport of the penetrant is therefore solely by
passive diffusion, which can be described by Fick's first law
(equation 1). The diffusion of a drug across the stratum corneum
(J.sub.S) is therefore the rate-determining step in skin
permeation. J s = D K C v L ( 1 ) ##EQU1##
[0114] Where J.sub.S represents the flux of the permeant across the
membrane; D is the diffusion coefficient of the penetrant in the
membrane; K, the stratum corneum-vehicle partition coefficient;
C.sub.v, the concentration of the penetrant in the vehicle; and L
the diffusional path length across the membrane. J.sub.S was
determined from the linear portions of the permeation profile
obtained from the infinite dose study as in accordance with Fick's
law. Permeability coefficient (K.sub.P) which is a product of (D, K
and L) was calculated as J.sub.S/C.sub.v. The lag time (T.sub.L)
was determined by the intercept of the linear portions of the skin
permeation profile on the x-axis where applicable. Enhancement
factors (EF) were calculated as a ratio of flux of permeant through
treated skin to that of untreated skin. All data reported represent
a mean of n.gtoreq.3-6 and its standard deviation (s.d.) or error
(s.e.) except otherwise stated. Statistical analysis was conducted
using the analysis of variance method (ANOVA) and student's t-test,
the level of significance was taken at p.ltoreq.0.05.
Results and Discussion
Optimisation Studies
[0115] The infinite dose method was used to investigate the
relationship between the nature of bristles, pressure (weight)
exerted on membrane and treatment time on permeation of the 3
markers. This was then compared to already established methods of
skin penetration enhancement. The rotational speed of the brush was
maintained at 80 rpm for each experiment. The limitation of using
the soft bristles (brush A) included the fact that the length of
the bristles at the periphery of the brush were slightly longer
than those in the middle. Therefore, the surface of the brush was
not uniform. Hence at low pressures (300 Nm.sup.-2) only the
peripheral bristles were in contact with the skin, so that
pressures.gtoreq.450 Nm.sup.-2 were used, in order to ensure
maximum contact with skin on using brush A. As a result of the flat
nature of the surface of brush B (hard bristles) such problems were
not experienced, thereby more readily allowing the assessment of
pressures at 300 Nm.sup.-2.
Permeation of MP, BP & CF (Using Soft Bristles)
[0116] The human skin used in experiments involving brush A was
from the same donor. FIGS. 1a-c show the effect of using the device
with brush A (soft bristles) at different pressures and treatment
times for the different permeants. A minimum threshold pressure of
450 Nm.sup.-2 and a maximum treatment time of 45 s was
employed.
[0117] In FIG. 1a, which shows the effect of rotating brush A on
skin permeation profile of CF: (.diamond.) untreated skin;
(.box-solid.) 450 N m.sup.-2, 20 s; (X) 450 N m.sup.-2, 45 s;
(.DELTA.) 750 N m.sup.-2, 45 s; (.diamond-solid.) 1200N m.sup.-2,
45 s. Data represents, mean.+-.s.d. (n=3-6). Device speed
maintained at 80 rpm
[0118] In FIG. 1b, which shows the effect of rotating device brush
A on skin permeation profile of BP: (.diamond.) untreated skin;
(.box-solid.) 450 N m.sup.-2, 20 s; (X) 450 N m.sup.-2, 45 s;
(.DELTA.) 750 N m.sup.-2, 45 s; (.diamond-solid.) 1200 N m.sup.-2,
45 s. Data represents, mean+.+-.s.d. (n=3-6). Device speed
maintained at 80 rpm
[0119] In FIG. 1c, which shows the effect of rotating device brush
A on skin permeation profile of MP: (.diamond.) untreated skin; (X)
450 N m.sup.-2, 45 s; (.diamond-solid.) 1200 N m.sup.-2, 45 s. Data
represents, mean.+-.s.d. (n=3-6). Device speed maintained at 80
rpm.
[0120] Where an enhancement factor (EF) of 2 or more was observed
(i.e. significantly different from control) the use of a shorter
treatment time of 20 s was investigated (c.f. CF--Table 4a and
BP--Table 4b, below). The CF fluxes observed under conditions of
450 Nm.sup.-2, 20 s, were however not significantly different from
that of untreated skin. An increase in treatment time from 20 s to
45 s at constant pressure was found to generally increase the flux
of all the markers. The use of brush A was found to enhance the
permeation of all the markers by at least an average factor of 2
(Tables 4a-c). Enhancement factors recorded were in the order of
CF.gtoreq.BP.gtoreq.MP. Increasing the pressure exerted on the
membrane was found to enhance permeation. However, no significant
differences (p.gtoreq.0.05) were observed in flux between 450
Nm.sup.-2 and 1200 Nm.sup.-2 at a treatment time of 45 s. This may
be due to the fact that, at weights greater than 450 Nm.sup.-2, the
nature of the bristles of brush A becomes a limiting factor, such
that further increase in applied pressure did not yield an increase
in flux. TABLE-US-00005 TABLE 4a Effect of treatment on in vitro
skin permeation parameters of CF using brush A J.sub.S K.sub.P
T.sub.L Skin treatment (10.sup.-4 .mu.g/cm/s) (10.sup.-8 cm/s)
(min) EF Untreated 6.96 .+-. 1.53 3.39 .+-. 0.75 77.66 .+-. 12.96
-- 450 Nm.sup.-2/ 10.3 .+-. 2.67.sup.p 5.04 .+-. 1.30 68.33 .+-.
17.76 1.47 20 s 450 Nm.sup.-2/ 16.3 .+-. 0.86* 7.95 .+-. 0.42 41.21
.+-. 8.09 2.34 45 s 750 Nm.sup.-2/ -- -- -- -- 45 s 1200 Nm.sup.-2/
18.4 .+-. 8.93* 8.97 .+-. 4.06 16.74 .+-. 6.50 2.64 45 s
Delipidised 52.25 .+-. 25.17* 25.66 .+-. 12.28 4.19 .+-. 1.39 7.47
Data represents mean .+-. s.d. (n .gtoreq. 3) except where
otherwise stated. .sup.prepresents n = 2 *Flux significantly
different from that of untreated skin (p .ltoreq. 0.05). Device
speed maintained at 80 rpm.
[0121] TABLE-US-00006 TABLE 4b Effect of treatment on in vitro skin
permeation parameters of BP using brush A J.sub.S K.sub.P T.sub.L
Skin treatment (10.sup.-3 .mu.g/cm/s) (10.sup.-5 cm/s) (min) EF
Untreated 3.80 .+-. 0.46 1.90 .+-. 0.23 33.47 .+-. 8.79 -- 450
Nm.sup.-2, 20 s 6.60 .+-. 0.49* 3.30 .+-. 0.25 37.10 .+-. 2.26 1.74
450 Nm.sup.-2, 45 s 7.50 .+-. 0.75* 3.75 .+-. 0.37 25.22 .+-. 2.17
1.97 750 Nm.sup.-2, 45 s 8.26 .+-. 0.89* 4.13 .+-. 0.45 26.34 .+-.
1.48 2.17 1200 Nm.sup.-2, 45 s 8.62 .+-. 1.05* 4.31 .+-. 0.52 26.39
.+-. 1.30 2.26 Delipidised 15.95 .+-. 1.55* 7.98 .+-. 0.78 18.58
.+-. 3 4.20 Data represents mean .+-. s.d. (n .gtoreq. 3) except
where otherwise stated. *Flux significantly different from that of
untreated skin (p .ltoreq. 0.05). Device speed maintained at 80
rpm.
[0122] TABLE-US-00007 TABLE 4c Effect of treatment on in vitro skin
permeation parameters of MP using brush A. J.sub.S K.sub.P T.sub.L
Skin treatment (10.sup.-3 .mu.g/cm/s) (10.sup.-6 cm/s) (min) EF
Untreated 7.46 .+-. 0.67 3.83 .+-. 0.35 16.61 .+-. 5.15 -- 450
Nm.sup.-2, 9.78 .+-. 0.54* 5.02 .+-. 0.27 16.12 .+-. 4.45 1.31 45 s
750 Nm.sup.-2, -- -- -- -- 45 s 1200 Nm.sup.-2, 11.16 .+-. 1.60*
5.74 .+-. 0.83 12.43 .+-. 5.46 1.50 45 s Delipidised 28.40 .+-.
0.29* 14.59 .+-. 1.48 3.87 .+-. 2.09 3.81 Data represents mean .+-.
s.d. (n .gtoreq. 3) except where otherwise stated. *Flux
significantly different from that of untreated skin (p .ltoreq.
0.05). Device speed maintained at 80 rpm.
[0123] The hydrophilic nature of CF results in very long lag times,
as observed in this experiment (.about.70 min) with untreated skin.
The effect of the device on the lag times was profound in the case
of CF, with altering either the pressure or duration of treatment
significantly reducing the lag times by .about.75% of their
original value. The use of delipidised skin was also found to be
more effective than use of the device with brush A in enhancing
permeation of the 3 markers. The lower EF's recorded for the
parabens, compared to CF, signifies the relative ease at which such
lipophilic markers permeate the SC, either in the absence or
presence of skin lipids.
[0124] The electron micrographs obtained (not shown) demonstrated
some disruption (attrition) of the Stratum corneum and the
associated loosening of these layers. Such perturbation possibly
creates channels/disruptions in the membrane, which may account for
the increase in flux of the permeants. Disruption is restricted
within the upper layers of the skin, whilst the remainder of the
epidermis is unaffected. Enhancement factors less of 2 recorded in
this part of the study prompted the use of harder bristles (brush
B) in order to further enhance skin permeation.
Permeation of CF, MP and BP using Harder Bristles (Brush B)
[0125] Surface analysis of the epidermis by electron microscopy
showed that the extent of barrier disruption or perturbation
induced by the device, on using brush B, was slightly greater than
that of brush A (data not shown)
[0126] Release profiles shown in FIGS. 2a-c, (Data in Tables 5a-c,
below) depict the effect of bristle type on skin absorption of the
3 markers. A minimum threshold pressure of 300 Nm.sup.-2 and a
maximum treatment time of 45 s was employed. Significant
differences (p.gtoreq.0.05) in penetrant flux across human
epidermal sheets on using brush B relative to brush A was observed
for all permeants.
[0127] In FIG. 2a, which shows the effect of rotating device brush
A and B on skin permeation of CF; (.box-solid.) untreated skin
(.quadrature.) brush A at 300 N m.sup.-2, 45 s; (+) brush B at 300
N m.sup.-2, 15 s; (.tangle-solidup.) brush B at 300 N m.sup.-2, 25
s. Data represents, mean.+-.s.d. (n=3-6). Device speed maintained
at 80 rpm. Skin donor used for CF different from that used for MP
and BP in FIGS. 2b-c.
[0128] In FIG. 2b, which shows the effect of rotating device brush
A and B on skin permeation of MP; (.box-solid.) untreated skin
(.quadrature.) brush A at 300 N m.sup.-2, 45 s; (.tangle-solidup.)
brush B at 300 N m.sup.-2, 25 s; (.DELTA.) brush B at 450 N
m.sup.-2, 15 s. Data represents, mean.+-.s.d. (n=3-6). Device speed
maintained at 80 rpm.
[0129] In FIG. 2c, which shows the effect of rotating device brush
A and B on skin permeation of BP; (.box-solid.) untreated skin
(.quadrature.) brush A at 450 N m.sup.-2, 45 s; (+) brush B at 300
N m.sup.-2/15 s; (.tangle-solidup.) brush B at 300 N m.sup.-2, 25
s; (.DELTA.) brush B at 450 N m.sup.-2, 15 s. Data represents,
mean.+-.s.d. (n=3-6). Device speed maintained at 80 rpm.
[0130] The higher EF's recorded for brush B are likely to be
attributed to the degree of perturbation imposed on the membrane
relative to brush A (Tables 5a-c, below) with CF being most
markedly affected, with an increase in EF of between 37 and 64.
TABLE-US-00008 TABLE 5a Effect of treatment on in vitro permeation
parameters of CF using brush B J.sub.S K.sub.P T.sub.L Penetrant
Skin treatment (10.sup.-4 .mu.g/cm/s) (10.sup.-8 cm/s) (min) EF
CF.sup.X Untreated 1.87 .+-. 0.26 9.15 .+-. 1.27 19.69 .+-. 3.54 --
450 Nm.sup.-2, 45 s.sup.a 8.52 .+-. 0.29* 41.61 .+-. 14.19 16.74
.+-. 3.99 4.55 300 Nm.sup.-2, 25 s 120.92 .+-. 42.55*.sup.+ 589.93
.+-. 207.62 -- 64.44 300 Nm.sup.-2, 15 s 70.19 .+-. 34.87*.sup.+
342.4 .+-. 170.1 -- 37.41 450 Nm.sup.-2, 15 s -- -- -- --
Delipidised 20.43 .+-. 5.50*.sup.+ 99.68 .+-. 26.84 -- 10.93
Tapestripped 35.5 .+-. 29.5*.sup.+ 173.4 .+-. 144.0 17.16 .+-. 9.15
19.01 EtOH/PBS 28.98 .+-. 6.39*.sup.+ 141.4 .+-. 31.21 26.71 .+-.
9.26 15.46 Data represents mean .+-. s.d. (n .gtoreq. 3). *Flux
significantly different from untreated skin (p .ltoreq. 0.05).
.sup.aRepresents brush A. .sup.+Flux significantly different from
skin treated with brush A (p .ltoreq. 0.05). .sup.XSkin donor used
for CF different from that used for MP and BP in Tables 4b-c.
Device speed maintained at 80 rpm.
[0131] TABLE-US-00009 TABLE 5b Effect of treatment on in vitro
permeation parameters of MP using brush B J.sub.S K.sub.P T.sub.L
Penetrant Skin treatment (10.sup.-3 .mu.g/cm/s) (10.sup.-6 cm/s)
(min) EF MP Untreated 10.90 .+-. 1.28 5.14 .+-. 6.06 15.02 .+-.
3.74 -- 450 Nm.sup.-2, 45 s.sup.a 13.53 .+-. 0.95* 6.38 .+-. 0.45
6.18 .+-. 1.34 1.24 300 Nm.sup.-2, 25 s 50.16 .+-. 9.25*.sup.+
23.66 .+-. 4.36 3.29 .+-. 2.09 4.60 300 Nm.sup.-2, 15 s -- -- -- --
450 Nm.sup.-2, 15 s 62.34 .+-. 12.75*.sup.+ 29.41 .+-. 6.01 6.73
.+-. 3.63 5.72 Delipidised 41.98 .+-. 2.05*.sup.+ 19.81 .+-. 0.96
-- 3.85 Tapestripped 53.86 .+-. 12.27*.sup.+ 25.41 .+-. 5.79 2.71
.+-. 1.61 4.94 EtOH/PBS 44.45 .+-. 7.19*.sup.+ 20.96 .+-. 3.39 7.76
.+-. 5.56 4.08 Data in Table 5b represents mean .+-. s.d. (n
.gtoreq. 3). *Flux significantly different from untreated skin (p
.ltoreq. 0.05). .sup.aRepresents brush A. .sup.+Flux significantly
different from skin treated with brush A (p .ltoreq. 0.05).
[0132] TABLE-US-00010 TABLE 5c Effect of treatment on in vitro
permeation parameters of BP using brush B J.sub.S K.sub.P T.sub.L
Penetrant Skin treatment (10.sup.-4 .mu.g/cm/s) (10.sup.-5 cm/s)
(min) EF BP Untreated 4.93 .+-. 0.22 2.47 .+-. 0.11 35.84 .+-. 1.98
-- 450 Nm.sup.-2, 45 s.sup.a 8.38 .+-. 1.09* 4.19 .+-. 0.54 24.51
.+-. 5.50 1.69 300 Nm.sup.-2, 25 s 10.47 .+-. 0.96* 5.23 .+-. 0.48
23.06 .+-. 2.19 2.12 300 Nm.sup.-2, 15 s 6.16 .+-. 0.89* 3.08 .+-.
0.44 22.65 .+-. 3.22 1.25 450 Nm.sup.-2, 15 s 12.69 .+-.
2.07*.sup.+ 6.34 .+-. 1.03 14.55 .+-. 5.18 2.57 Delipidised 20.54
.+-. 2.85*.sup.+ 10.27 .+-. 1.43 8.17 .+-. 5.41 4.16 Tapestripped
15.60 .+-. 3.69*.sup.+ 7.80 .+-. 1.84 34.78 .+-. 4.44 3.16 EtoH/PBS
18.48 .+-. 1.61*.sup.+ 9.24 .+-. 0.80 26.43 .+-. 5.05 3.75 Data in
Table 5c represents mean .+-. s.d. (n .gtoreq. 3). *Flux
significantly different from untreated skin (p .ltoreq. 0.05).
.sup.aRepresents brush A. .sup.+Flux significantly different from
skin treated with brush A (p .ltoreq. 0.05).
[0133] The effect of brush B at 300 Nm.sup.-2 was found to increase
when treatment duration was increased from 15 s to 25 s. Shorter
treatment times and lower pressures were required in the use of
brush B, when compared to brush A, to produce significant changes
to the barrier nature of the SC and, therefore, drug flux. With CF,
significantly higher fluxes were observed with the use of brush B,
compared to the other enhancement methods, thus demonstrating the
benefit of this device for such molecules. In the case of the
parabens, the highest EF recorded on using the novel device was
comparable to the established and developmental modes of skin
permeation enhancement. Due to the remarkably high fluxes recorded
for CF with the use of brush B, the effect of increasing pressure
exerted (>300 Nm.sup.-2) on CF flux was not investigated
further.
CF Pseudo Finite Dose Study
[0134] This part of the study involved the use of the device with
brush B and the minimum and ideal conditions of pressure and a
variation in treatment time to further evaluate, via the finite
dose methodology, the effect of the system using CF (FIG. 3). This
was performed, in order to investigate the degree of enhancement
provided-by the device under application conditions more like those
that would occur in vivo. CF was selected as a suitable candidate
for this part of the study, due to its poor intrinsic permeability
across intact skin as well as for the promising results recorded
during the optimisation stages. For untreated skin, and chemical
enhancement procedures, the presence of CF was only determined
after 120 min (limit of detection of analytical method was 0.05
ug/ml).
[0135] In FIG. 3, which shows the results of the pseudo-finite dose
study comparing the effect of the device using brush B (300
Nm.sup.-2/25 s) to other established modes of skin permeation
enhancement; Mean.+-.s.d. (n=3-6). *Amount of CF in receptor after
120 min. Device speed maintained at 80 rpm.
[0136] Administered doses were found to dry into a thin film after
approximately 1 hr. The amount of CF deposited in the receptor
compartment of the Franz cell, with the use of the chemical
enhancement method, was found not to be significantly different
(p.gtoreq.0.05) from untreated skin. The amount of CF in receptor
after 30 min using brush B was found to be significantly higher
(p.ltoreq.0.05) and at least double that recorded for the other
methods of enhancement.
Permeation of ACV (Pseudo Finite Dose Study)
[0137] The poor efficacy of ACV topical preparations have been
attributed its poor skin permeability, resulting from its
hydrophilicity, which hinders it from reaching the target site of
the basal epidermis (Stagni et al., 2004). This, therefore, makes
ACV an interesting model candidate for the evaluation of a novel
transdermal device. The ability of the novel device to enhance the
flux profile of ACV from a commercial cream is demonstrated in
FIGS. 4-5 and in Table 6.
[0138] In FIG. 4, which shows the effect of treatment time on the
skin permeation profile of acyclovir from a topical preparation
(Zovirax.RTM.) using a device with brush B; (.box-solid.)
untreated; (.circle-solid.) 10 s; (.circle-solid. with dashed line)
30 s; (.tangle-solidup.) 60 s. Data represents mean+s.e. (n=4-9).
Constant device parameters (speed; 80 rpm, pressure; 300
Nm.sup.-2).
[0139] In FIG. 5, which shows a comparison of the effect of device
treatment duration and iontophoretic treatment on skin permeation
of radiolabelled .sup.3H-labelled acyclovir after 60 min. Mean 35
s.e. (n=4-9). Device speed maintained at 80 rpm, pressure; 300
Nm.sup.-2.
[0140] A significant increase in ACV flux across the skin was
observed as the brush treatment duration was increased,
demonstrating the increased benefit of the device on delivering
molecules like acyclovir across the skin. At maximum treatment
time, the device of the invention resulted in a ca. 600% increase
in enhancement factor, when compared to iontophoresis, also
operated under optimum conditions (Volpato et al., 1995, 1998;
Morrel et al., 2004). TABLE-US-00011 TABLE 6 Effect of using brush
B at different treatment times (10, 30 & 60 s) and
iontophoretic treatment on skin absorption of radiolabelled
acyclovir Amount in receptor after 60 min (.quadrature.g/cm.sup.2)
EF Untreated 0.14 .+-. 0.08 -- Brush treatment 10 s 5.06 .+-. 1.88*
36 30 s 12.5 .+-. 4.02* 89 60 s 30.91 .+-. 5.45* 220
Iontophoresis.sup.c 4.95 .+-. 2.35* 35 Data represents mean .+-.
s.d. (n = 4-9) except otherwise stated. *Flux significantly
different from that of untreated skin (p .ltoreq. 0.05). Constant
device parameters (speed; 80 rpm, pressure; 300 Nm.sup.-2).
.sup.cCathodal iontophoresis (not post iontophoresis) performed for
a period of 10 min, after which the current was switched off.
Permeation of Angiotensin II (Infinite Dose Study)
[0141] The highly significant results in skin permeation
enhancement observed for the hydrophilic solutes ACV and CF
prompted an investigation into the ability of the device to enhance
the permeation of a model peptide, Ang II. The hydrophilic nature
and large molecular weight of the peptide makes it an extremely
unlikely candidate to be absorbed across the skin.
[0142] It can be seen from FIG. 6 and Tables 7a and b, below, that
the use of all the enhancement techniques, with the exception of
post-iontophoresis, was found to significantly increase the
permeation of the model peptide, compared to untreated (intact)
skin at each defined time period (4 h and 24 h) although the effect
was greatest with the device of the invention.
[0143] In FIG. 6, which shows a comparison of the effect of a
device fitted with brush B with other enhancement strategies on the
skin permeation of Ang II over a (.quadrature.) 4 h and
(.box-solid.) 24 h period. Data represents mean.+-.s.d.
(n=3-6).
[0144] The amount of Ang II permeating the skin was generally found
to increase with time, however, this increase was found not to be
significant for untreated, post-iontophoretic and tape-stripped
skin. TABLE-US-00012 TABLE 7a Effect of using brush B and other
treatment methods on the in vitro skin permeation of Ang II after 4
h Amount in receptor after 4 h (ng/cm.sup.2) EF Untreated 0.27 .+-.
0.23 -- Post-iontophoresis 0.46 .+-. 0.15.sup.+ 1.7 Delipidisation
15.71 .+-. 2.85* 58 Tape-stripping 14.44 .+-. 4.73* 53 Rotating
brush 19.45 .+-. 0.55* 72 Data represents mean .+-. s.e. (n = 3-6)
except otherwise stated. *Significantly different from that of
untreated skin (p .ltoreq. 0.05). .sup.+7.53 .+-. 5.87 ng/cm.sup.2
was initially recorded (see FIG. 3), however this amount was found
not to be reproducible on sample re-analysis.
[0145] TABLE-US-00013 TABLE 7b Effect of using brush B and other
treatment methods on the in vitro skin permeation of Ang II after
24 h Amount in receptor after 24 h (ng/cm.sup.2) EF Untreated 1.69
.+-. 1.01 -- Post-iontophoresis 10.02 .+-. 6.28 6 Delipidisation
83.03 .+-. 24.28* 49 Tape-stripping 46.93 .+-. 15.62* 27 Rotating
brush 107.49 .+-. 19.66* 63 Data represents mean .+-. s.e. (n =
3-6) except otherwise stated. *Significantly different from that of
untreated skin (p .ltoreq. 0.05).
[0146] Thus, the above Example clearly demonstrates the ability of
the oscillating brush device of the invention to enhance in vitro
skin permeability and/or reduce lag times of permeants of differing
physicochemical properties across the skin, by the disruption of
the upper skin layers. The surprising benefits of this approach
when compared to established and developmental methods of
permeation enhancement, has also been clearly shown.
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* * * * *