U.S. patent application number 10/541019 was filed with the patent office on 2006-06-08 for agent improving proton-driven transporter-mediated absorption in digestive tract and process for producing the same.
Invention is credited to Masaaki Odomi, Yoshimichi Sai, Ikumi Tamai, Hidekazu Toyobuku, Akira Tsuji.
Application Number | 20060121107 10/541019 |
Document ID | / |
Family ID | 32709038 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060121107 |
Kind Code |
A1 |
Tsuji; Akira ; et
al. |
June 8, 2006 |
Agent improving proton-driven transporter-mediated absorption in
digestive tract and process for producing the same
Abstract
The present invention provides a pharmaceutical preparation that
can improve absorption of a pharmaceutical compound in the
gastrointestinal tract and that provides, through oral
administration or like method, a blood concentration from which
sufficient remedial effects can be expected, and a method for
producing such a preparation. The invention is directed to a
pharmaceutical preparation exhibiting excellent gastrointestinal
absorbability comprising a compound recognized by a proton-coupled
transporter and a pH-sensitive polymer in an amount sufficient for
the gastrointestinal tract to acquire a pH at which the
proton-coupled transporter optimally absorbs the compound into a
cell.
Inventors: |
Tsuji; Akira; (Kanazawa-shi,
JP) ; Tamai; Ikumi; (Kanazawa-shi, JP) ; Sai;
Yoshimichi; (Kanazawa-shi, JP) ; Odomi; Masaaki;
(Tokushima-shi, JP) ; Toyobuku; Hidekazu;
(Tokushima-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Family ID: |
32709038 |
Appl. No.: |
10/541019 |
Filed: |
January 8, 2004 |
PCT Filed: |
January 8, 2004 |
PCT NO: |
PCT/JP04/00070 |
371 Date: |
June 28, 2005 |
Current U.S.
Class: |
424/464 ;
514/423; 514/561; 514/57 |
Current CPC
Class: |
A61K 9/0053 20130101;
A61P 31/04 20180101; A61P 43/00 20180101; A61K 47/32 20130101; A61P
31/12 20180101; A61K 31/545 20130101; A61K 9/08 20130101; A61K
31/546 20130101; A61P 1/14 20180101; A61P 1/00 20180101; A61P 35/00
20180101 |
Class at
Publication: |
424/464 ;
514/423; 514/561; 514/057 |
International
Class: |
A61K 31/401 20060101
A61K031/401; A61K 31/198 20060101 A61K031/198; A61K 9/20 20060101
A61K009/20; A61K 31/716 20060101 A61K031/716 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 14, 2003 |
JP |
2003-6005 |
Claims
1. A pharmaceutical preparation exhibiting excellent
gastrointestinal absorbability comprising a compound recognized by
a proton-coupled transporter and a pH-sensitive polymer, the
pH-sensitive polymer being used in an amount sufficient to impart
the gastrointestinal tract a pH at which the proton-coupled
transporter optimally functions for cellular uptake of the
compound.
2. A pharmaceutical preparation according to claim 1, wherein the
proton-coupled transporter is an influx transporter expressed in a
small-intestinal epithelial cell.
3. A pharmaceutical preparation according to claim 2, wherein the
proton-coupled transporter is one member selected from the group
consisting of a peptide transporter, monocarboxylic acid
transporter, and D-cycloserine-transporting amino acid
transporter.
4. A pharmaceutical preparation according to claim 3, wherein the
proton-coupled transporter is a peptide transporter.
5. A pharmaceutical preparation according to claim 4, wherein the
compound recognized by the peptide transporter is at least one
species selected from the group consisting of peptides,
.beta.-lactam antibiotics, angiotensin-converting enzyme
inhibitors, antiviral agents, antitumor agents, and .omega.-amino
carboxylic acids.
6. A pharmaceutical preparation according to claim 3, wherein the
proton-coupled transporter is a monocarboxylic acid
transporter.
7. A pharmaceutical preparation according to claim 6, wherein the
compound recognized by the monocarboxylic acid transporter is at
least one species selected from the group consisting of lactic
acid, pyruvic acid, acetic acid, propionic acid, butyric acid,
glycolic acid, nicotinic acid, salicylic acid, benzoic acid,
p-aminobenzoic acid, and foscarnet.
8. A pharmaceutical preparation according to claim 3, wherein the
proton-coupled transporter is an amino acid transporter
transporting D-cycloserine.
9. A pharmaceutical preparation according to claim 8, wherein the
compound recognized by the amino acid transporter transporting
D-cycloserine is at least one species selected from the group
consisting of L-alanine, .beta.-alanine, L-proline, and glycin.
10. A pharmaceutical preparation according to claim 1, wherein the
pH at which the proton-coupled transporter optimally functions for
cellular uptake of the compound is determined by evaluating under
various pH conditions the extent of cellular uptake of the compound
using cells in which the proton-coupled transporter is
expressed.
11. A pharmaceutical preparation according to claim 1, wherein the
pH at which the proton-coupled transporter optimally functions for
cellular uptake of the compound is determined by measuring the
extent of the compound migrated within the gastrointestinal tract
using the in situ closed loop method conducted in the intestinal
tract.
12. A pharmaceutical preparation according to claim 1, wherein the
pH-sensitive polymer is at least one species selected from the
group consisting of dried methacrylic acid copolymer, methacrylic
acid copolymer LD, methacrylic acid copolymer L, methacrylic acid
copolymer S, polyacrylic acid, maleic acid/n-alkyl vinyl ether
copolymer, hydroxypropylmethylcellulose acetate succinate, and
hydroxypropylmethylcellulose phthalate.
13. A pharmaceutical preparation according to claim 1, wherein the
pH-sensitive polymer is at least one species selected from the
group consisting of Eudragit L100-55, Eudragit 30D-55, Eudragit
L100, Eudragit S100, Eudragit P-4135F, polyacrylic acid, maleic
acid/n-alkyl vinyl ether copolymer, hydroxypropylmethylcellulose
acetate succinate, and hydroxypropylmethylcellulose phthalate.
14. A pharmaceutical preparation according to claim 1 that is used
for oral administration.
15. A method for formulating a pharmaceutical preparation having
excellent gastrointestinal absorbability comprising the steps of:
(1) determining a pH at which the proton-coupled transporter
optimally transports a compound recognized by the proton-coupled
transporter into a cell is; and (2) adding to the compound a
pH-sensitive polymer in an amount sufficient to impart the optimum
pH for cellular uptake of the compound.
16. A pharmaceutical preparation formulated according to the method
of claim 15.
17. A pharmaceutical preparation for enhancing gastrointestinal
absorbability of a compound recognized by a proton-coupled
transporter, the pharmaceutical preparation comprising the compound
and a pH-sensitive polymer in an amount sufficient for the
gastrointestinal tract to acquire a pH at which the proton-coupled
transporter optimally transports the compound into a cell.
18. A method for enhancing gastrointestinal absorbability of a
compound recognized by a proton-coupled transporter, the method
comprising conditioning the gastrointestinal tract to a pH at which
the proton-coupled transporter optimally transports the compound
into a cell.
19. A method for using a pH-sensitive polymer, to enhance
gastrointestinal absorbability of a compound recognized by a
proton-coupled transporter, in an amount sufficient to impart to
the gastrointestinal tract a pH at which the proton-coupled
transporter optimally transports the compound into a cell.
20. (canceled)
21. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a gastrointestinal
absorption enhancer mediated by a proton-coupled transporter and a
method for preparing it.
BACKGROUND OF THE INVENTION
[0002] For many chronically diseased areas, oral administration is
generally considered as a desirable route of pharmaceutical
administration in view of convenience and cost. However, many
candidate compounds for medicinal products exhibit low
absorbability when administered orally since they have a low
membrane permeability in the gastrointestinal tract or they are
unstable therein, thereby facing a condition of being unable to
maintain the blood concentration for sufficient pharmacological
effects.
[0003] Moreover, it is known that there are some organic compounds
that show a tendency of being barely absorbed although they are
reported to be recognized by influx transporters expressed in
small-intestinal epithelial cells (for example, Sakamato et al., J.
Antibiot. 38 (1985): 496-504, and Kelly et al., Clin.
Pharmacokinet. 19 (1990): 177-196, etc.).
[0004] Given this circumstance, research has been conducted in
using various absorption enhancers and enzyme inhibitors to improve
the absorption of compounds that are candidates for medical
products. For example, Swenson et al., (Adv. Drug Del. Rev. 8
(1992): 39-92) and Kompella et al., (Adv. Drug Del. Rev. 46 (2001):
211-245) disclose methods for using absorption enhancers to improve
peptide absorption. However, these methods pose the problem of cell
damage by the absorption enhancers, which are primarily added to
enhance absorption.
[0005] Hayakawa et al., (Pharm. Res. 9 (1992): 535-540) and Zhou et
al., (J. Control Rel. 29 (1994): 239-252) teach methods for adding
enzyme inhibitors to inhibit decomposition and promote absorption
in the gastrointestinal tract. However, these methods cause
problems such that no substrate specificity is obtained in
absorption.
[0006] Furthermore, to improve absorption of furosemide, which is
recognized by an efflux transporter in the gastrointestinal tract,
addition of a pH-sensitive polymer is known (e.g., Terao et al. J.
Pharm. Pharmacol. 53 (2000): 433-440). However, this reference does
not suggest the use of transporters to improve gastrointestinal
absorption, and has, as with the prior art methods described above,
the problem of not imparting substrate specificity to
gastrointestinal absorption.
[0007] In addition, there have been no prior art methods that
enhance the absorption of organic compounds that are, despite being
substrates for influx transporters, of poor absorbability.
DISCLOSURE OF THE INVENTION
[0008] An object of the invention is to provide a pharmaceutical
preparation that can improve cellular absorption of a
pharmaceutical composition and that can provide, through oral
administration or like method, a blood concentration from which
sufficient remedial effects can be expected, and to provide a
method for producing such a preparation. Specifically, an object of
the invention is to provide a pharmaceutical preparation having an
excellent gastrointestinal absorbability comprising a compound
recognized by a proton-coupled transporter and a pH-sensitive
polymer in an amount sufficient to give a desirable pH at which the
proton-coupled transporter optimally transports the compound into a
cell in the gastrointestinal tract, and a production method
thereof.
[0009] The inventors conducted extensive research to solve the
aforementioned problems and found the facts described in (1) and
(2) below:
[0010] (1) Compounds recognized by peptide transporters
(hereinafter sometimes referred to as "substrates"), which is one
type of the proton-coupled transporters, sometimes exhibit a
tendency to be gastrointestinally poorly absorbed because the
amount of protons (H.sup.+), which are the driving force of peptide
transporters for transporting substrates, is reduced as they travel
to the lower gastrointestinal tract, and the ability of substrate
transportation is thereby reduced; and
[0011] (2) By adding a specific amount of pH-sensitive polymers to
the substrate, the driving force of peptide transporters is
increased and the gastrointestinal absorption of substrates having
a tendency to be poorly absorbed is improved.
[0012] The inventors carried out further development based on these
findings and found that cellular uptake of a substrate is most
enhanced at the pH optimum for the proton-coupled transporter. The
present invention was accomplished based on these findings.
[0013] In particular, the present invention provides the
following:
[0014] Item 1. A pharmaceutical preparation exhibiting excellent
gastrointestinal absorbability comprising a compound recognized by
a proton-coupled transporter and a pH-sensitive polymer,
[0015] the pH-sensitive polymer being used in an amount sufficient
to impart the gastrointestinal tract a pH at which the
proton-coupled transporter optimally functions for cellular uptake
of the compound.
[0016] Item 2. A pharmaceutical preparation according to Item 1,
wherein the proton-coupled transporter is an influx transporter
expressed in a small-intestinal epithelial cell.
[0017] Item 3. A pharmaceutical preparation according to Item 2,
wherein the proton-coupled transporter is one member selected from
the group consisting of a peptide transporter, monocarboxylic acid
transporter, and D-cycloserine-transporting amino acid
transporter.
[0018] Item 4. A pharmaceutical preparation according to Item 3,
wherein the proton-coupled transporter is a peptide
transporter.
[0019] Item 5. A pharmaceutical preparation according to Item 4,
wherein the compound recognized by the peptide transporter is at
least one species selected from the group consisting of peptides,
.beta.-lactam antibiotics, angiotensin-converting enzyme
inhibitors, antiviral agents, antitumor agents, and .omega.-amino
carboxylic acids..omega.
[0020] Item 6. A pharmaceutical preparation according to Item 3,
wherein the proton-coupled transporter is a monocarboxylic acid
transporter.
[0021] Item 7. A pharmaceutical preparation according to Item 6,
wherein the compound recognized by the monocarboxylic acid
transporter is at least one species selected from the group
consisting of lactic acid, pyruvic acid, acetic acid, propionic
acid, butyric acid, glycolic acid, nicotinic acid, salicylic acid,
benzoic acid, p-aminobenzoic acid, and foscarnet.
[0022] Item 8. A pharmaceutical preparation according to Item 3,
wherein the proton-coupled transporter is an amino acid transporter
transporting D-cycloserine.
[0023] Item 9. A pharmaceutical preparation according to Item 8,
wherein the compound recognized by the amino acid transporter
transporting D-cycloserine is at least one species selected from
the group consisting of L-alanine (.alpha.-alanine),
.beta.-alanine, L-proline, and glycin.
[0024] Item 10. A pharmaceutical preparation according to Item 1,
wherein the pH at which the proton-coupled transporter optimally
functions for cellular uptake of the compound is determined by
evaluating under various pH conditions the extent of cellular
uptake of the compound using cells in which the proton-coupled
transporter is expressed.
[0025] Item 11. A pharmaceutical preparation according to Item 1,
wherein the pH at which the proton-coupled transporter optimally
functions for cellular uptake of the compound is determined by
measuring the extent of the compound migrated within the
gastrointestinal tract using the in situ closed loop method.
[0026] Item 12. A pharmaceutical preparation according to Item 1,
wherein the pH-sensitive polymer is at least one species selected
from the group consisting of dried methacrylic acid copolymer,
methacrylic acid copolymer LD, methacrylic acid copolymer L,
methacrylic acid copolymer S, polyacrylic acid, maleic acid/n-alkyl
vinyl ether copolymer, hydroxypropylmethylcellulose acetate
succinate, and hydroxypropylmethylcellulose phthalate.
[0027] Item 13. A pharmaceutical preparation according to Item 1,
wherein the pH-sensitive polymer is at least one species selected
from the group consisting of Eudragit L100-55, Eudragit 30D-55,
Eudragit L100, Eudragit S100, Eudragit P-4135F, polyacrylic acid,
maleic acid/n-alkyl vinyl ether copolymer,
hydroxypropylmethylcellulose acetate succinate, and
hydroxypropylmethylcellulose phthalate.
[0028] Item 14. A pharmaceutical preparation according to any of
Items 1 to 13 that is used for oral administration.
[0029] Item 15. A method for formulating a pharmaceutical
preparation having excellent gastrointestinal absorbability
comprising the steps of:
[0030] (1) determining a pH at which the proton-coupled transporter
optimally transports a compound recognized by the proton-coupled
transporter into a cell; and
[0031] (2) adding to the compound a pH-sensitive polymer in an
amount sufficient to impart the pH optimum for cellular uptake of
the compound.
[0032] Item 16. A pharmaceutical preparation formulated according
to the method of Item 15.
[0033] Item 17. A pharmaceutical preparation for enhancing
gastrointestinal absorbability of a compound recognized by a
proton-coupled transporter,
[0034] the pharmaceutical preparation comprising the compound and a
pH-sensitive polymer in an amount sufficient for the
gastrointestinal tract to acquire a pH at which the proton-coupled
transporter optimally transports the compound into a cell.
[0035] Item 18. A method for enhancing gastrointestinal
absorbability of a compound recognized by a proton-coupled
transporter,
[0036] the method comprising conditioning the gastrointestinal
tract to a pH at which the proton-coupled transporter optimally
transports the compound into a cell.
[0037] Item 19. A method for using a pH-sensitive polymer, to
enhance gastrointestinal absorbability of a compound recognized by
a proton-coupled transporter, in an amount sufficient to impart to
the gastrointestinal tract a pH at which the proton-coupled
transporter optimally transports the compound into a cell.
[0038] Item 20. Use of a pH-sensitive polymer, to enhance
gastrointestinal absorbability of a compound recognized by a
proton-coupled transporter, in an amount sufficient to impart to
the gastrointestinal tract a pH at which the proton-coupled
transporter optimally transports the compound into a cell.
[0039] Item 21. Use of a pH-sensitive polymer, for formulating a
pharmaceutical preparation having an enhanced gastrointestinal
absorbability of a compound recognized by a proton-coupled
transporter, in an amount sufficient to impart to the
gastrointestinal tract a pH at which the proton-coupled transporter
optimally transports the compound into a cell.
DETAILED DESCRIPTION OF THE INVENTION
[0040] The present invention is directed to a pharmaceutical
preparation exhibiting excellent gastrointestinal absorbability
comprising a compound recognized by a proton-coupled transporter
(substrate) and a pH-sensitive polymer. The pharmaceutical
preparation comprises the pH-sensitive polymer in an amount
sufficient for the gastrointestinal tract to acquire a pH at which
the proton-coupled transporter optimally transports the substrate
into a cell.
[0041] The present invention is described hereinbelow in more
detail.
Proton-Coupled Transporters
[0042] The proton-coupled transporters of the invention refer to
active transporters that transport substrates from the mammalian
(especially, of humans) gastrointestinal tract into cells by taking
advantage of the proton (H.sup.+) gradient. Proton-coupled
transporters are expressed within the gastrointestinal tract and
the like, and, specifically, adjacent to the surface of the brush
border membranes of the gastrointestinal tract (especially, the
surface of the brush border membranes of small-intestinal
epithelial cells). They are influx transporters actively
transporting nutrients and medicaments into cells. The
aforementioned small intestine includes the duodenum, jejunum and
ileum.
[0043] Specific examples of proton-coupled transporters herein
include peptide transporters (PEPT), monocarboxylic acid
transporters, amino acid transporters transporting D-cycloserine,
and the like.
[0044] The aforementioned peptide transporters (PEPT) serve to
transport dipeptides, tripeptides, and similar compounds and
contribute in a living body to absorbing proteins and maintaining
peptidergic nitrogen sources. Specifically, examples thereof are
peptide transporter 1 (PEPT1), which is composed of 710 amino acids
and expressed mainly in the small intestine and kidney, and peptide
transporter 2 (PEPT2), which is composed of 729 amino acids and
expressed mainly in the kidney, brain, lung, spleen, etc.
[0045] Compounds absorbed into small-intestinal epithelial cells
via influx transporters are further transported into the blood via
basolateral peptide transporters present in the basolateral
membranes of small-intestinal epithelial cells. Basolateral peptide
transporters are facilitated diffusion transporters that serve to
transport in accordance with the concentration gradient.
[0046] Monocarboxylic acid transporters transport lactic acid and
contribute to maintenance of lactic acid, which is the final
product of anaerobic glycolysis, in a living body.
[0047] Amino acid transporters transporting D-cycloserine transport
amino acids and contribute to maintenance of amino acid in a living
body.
Compounds Recognized by Proton-Coupled Transporters
(Substrates)
[0048] Compounds recognized by proton-coupled transporters herein
refer to compounds that can be recognized by the aforementioned
proton-coupled transporters and taken up into cells (eg.
small-intestinal epithelial cells) from the gastrointestinal tract.
Whether compounds can be recognized by the proton-coupled
transporters or not is, for example, evaluated as follows:
[0049] The extent of cellular uptake of the compound is measured
using cells in which a target proton-coupled transporter is
expressed and cells in which no target transporter is expressed.
When uptake into cells in which the target proton-coupled
transporter is expressed is greater than in cells in which the
transporter is not expressed, it is considered that the
proton-coupled transporter is involved in the migration of the
compound into the cells.
[0050] Cells in which a proton-coupled transporter is expressed
herein denote those in which a proton-coupled transporter is
endogenously expressed. Examples of cells endogenously expressing a
proton-coupled transporter include Caco-2 cells, HT-29 cells,
COLO-320 cells, HT-1080 cells, AsPc-1 cells, Capan-2 cells,
SK-ChA-1 cells, etc.
[0051] Furthermore, using cells in which cellular uptake of the
aforementioned compound has been observed, the aforementioned
compound and another compound which is known to be recognized by a
proton-coupled transporter (e.g., cefadroxil (CDX)) are
simultaneously introduced to the test solutions, and cellular
uptake of the former compound is then evaluated. If an inhibitory
effect on the cellular uptake of the former compound is observed,
this compound is considered to be recognized by the proton-coupled
transporter.
[0052] The extent of cellular uptake of the compound can also be
measured once cells in which a proton-coupled transporter is
expressed are prepared. Such cells can be prepared according to
known methods. For example, PEPT1 cDNA is incorporated into a
mammalian cultured cell expression vector and an excessive amount
of transporter is expressed in model cells (e.g., Hela cells) after
transfection of the vector containing PEPT1 cDNA.
[0053] The extent of cellular uptake of a compound is evaluated,
using cells in which a proton-coupled transporter is expressed and
cells in which no proton-coupled transporter is expressed, by
measuring the amount of the compound absorbed into cells per unit
weight of cellular protein (the weight of the compound absorbed
into cells relative to the total weight of protein contained in
cells). For example, as for peptide transporters, it is evaluated
using cells in which a proton-coupled transporter is expressed and
cells in which no proton-coupled transporter is expressed, by
measuring the amounts of the compound absorbed into cells per unit
weight of cellular protein (.mu.L/mg protein), comparing the
amounts of the compound absorbed into transporter-expressed cells
with those of transporter-unexpressed cells, and determining the
extent of transporter absorption.
[0054] Among proton-coupled transporters, the aforementioned
peptide transporters (PEPT) have broader substrate specificity than
other nutrient transporters. Examples of compounds that are
recognized by PEPT (especially by PEPT1) and absorbed into
small-intestinal epithelial cells therefore include, in addition to
peptides, .beta.-lactam antibiotics, angiotensin-converting enzyme
inhibitors, antiviral agents, antitumor agents, and .omega.-amino
carboxylic acids, and a wide variety of other pharmaceutical
compounds.
[0055] Specific examples of peptides are dipeptides and
tripeptides. Dipeptides are not limited insofar as they are
obtained by amide-coupling a pair of amino acids randomly selected
from naturally- or synthetically-occurring amino acids. Preferable
among these are glycylsarcosine, carnosine, lisinopril, etc.
Tripeptides are not limited insofar as they are obtained by
amide-coupling three amino acids randomly selected from naturally-
or synthetically-occurring amino acids. Preferable examples among
these are Phe-Cys-Val, Glu-His-Pro, Phe-Ala-Pro, etc.
[0056] Examples of .beta.-lactam antibiotics include penicillin
antibiotics, cephem antibiotics, and the like. Specific examples
are amoxicillin, ampicillin, ciclacillin, phenoxymethylpenicillin,
propicillin, carfecillin, carbenicillin, bacampicillin,
pivampicillin, cefadroxil, cefixime, ceftibuten, cephaclor,
cephalexin, cephradine, SCE-100, cefatrizine, cephalothin,
cefdinir, loracarobef, FK089, latamoxef, pivcefalexine, cefazolin,
cefoperazone, cefoxitin, cefotiam, cefinetazole, etc.
[0057] Examples of angiotensin-converting enzyme inhibitors include
captopril, enalapril, quinapril, benazepril, fosinopril,
lisinopril, SQ 29852, enalaprilat, quinaprilat, benazeprilat,
fosinoprilat, and the like.
[0058] Examples of antiviral agents are valacyclovir and the
like.
[0059] Examples of antitumor agents are bestatin and the like.
[0060] Examples of .omega.-amino carboxylic acids include compounds
represented by General Formula (1):
H.sub.2N--(CH.sub.2).sub.n--COOH (1) wherein n is an integer from 4
to 11.
[0061] Other examples are L-dopa-L-phenylalanine, 4-aminophenyl
acetic acid (4-APAA), .delta.-aminolevulinic acid (ALA), etc.
[0062] Examples of compounds recognized by the aforementioned
monocarboxylic acid transporters of proton-coupled transporters and
absorbed into cells include lactic acid, pyruvic acid, acetic acid,
propionic acid, butyric acid, glycolic acid, nicotinic acid,
salicylic acid, benzoic acid, p-aminobenzoic acid, foscarnet,
etc.
[0063] Examples of compounds recognized by the aforementioned
D-cycloserine-transporting amino-acid transporters of
proton-coupled transporters and absorbed into cells include
L-alanine, .beta.-alanine, L-proline, glycine, etc.
pH Profiles of Substrates
[0064] The pH profile of a compound recognized by a proton-coupled
transporter (substrate) herein refers to the characteristics of
cellular uptake of the substrate effected by a proton-coupled
transporter under varying pH conditions (characteristics of
cellular absorption depending on pH conditions). Based on the pH
profile, the optimum pH can be obtained for a specific
proton-coupled transporter to transport a specific substrate into
cells.
[0065] The extent of cellular uptake of a substrate under various
pH conditions (the amount of substrate absorption into cells) can
be measured as follows: Using cells in which a proton-coupled
transporter is expressed, the extent of cellular uptake of a
substrate is measured in vitro under various pH conditions. For
example, the pH profile of substrates recognized by PEPT1 can be
obtained by measuring in vitro under various pH conditions (e.g.,
pHs from about 5.4 to about 7.5) the extent of cellular uptake of
the substrates, using cells expressing PEPT1 such as human colon
cancer-derived Caco-2 cells, which are gastrointestinal tract model
cells.
[0066] Specifically, measurement can be conducted according to a
method already reported (Tsuji, A., Takanaga, H., Tamai, I., and
Terasaki, T. "Transcellular Transport of Benzoic Acid Across Caco-2
Cells by a pH-Dependent and Carrier-Mediated Transport Mechanism".
Pharm. Res. 11 (1994): 30-37. (see, for example, Example 1)
[0067] Cellular absorption in vitro can be a guideline for
evaluating in vivo membrane permeability in the gastrointestinal
tract. The pH of the gastrointestinal tract in humans under
physiological conditions is reported to be 5.4 to 7.5 (Davies, B.,
and Morris, T. "Physiological Parameters in Laboratory Animals and
Humans". Pharm. Res. 10 (1993): 1093-1095). Absorption in the
gastrointestinal tract in vivo is therefore considered to occur
under these pH conditions.
[0068] The extent of cellular uptake of a substrate under various
pH conditions can also be estimated by measuring the amount of the
substrate absorbed into the gastrointestinal tract under various pH
conditions using a rat gastrointestinal tract loop, e.g.,
intestinal loop (in situ closed loop method). When a rat
gastrointestinal tract loop is used, the measurement can be
conducted in reference to the following reports: Barr, W. H., and
Riegelman, S. "Intestinal Drug Absorption and Metabolism I.
Comparison of Methods and Models to Study Physiological Factors of
In Vitro and In Vivo Intestinal Absorption". J. Pharm. Sci. 59
(1970): 154-163; and Hironori Yoshitomi. "Fundamental Experiment on
Gastrointestinal Absorption". Biopharmaceutics Experimental Manual.
Shigeru Goto (editor). Tokyo: Seishi Syoin, 1985: 2-22.
[0069] For example, rats are anesthetized by intraperitoneally
administering pentobarbital sodium (50 mg/kg). Then, laparotomy is
performed along the median line to expose the intestinal tract, and
a loop is formed at the ileum (e.g., FIG. 6). MES buffer containing
medical fluid and a polymer (5 mM KCl, 100 mM NaCl, 10 mM
2-(N-morpholino)ethanesulfonic acid (MES), 85 mM mannitol, 0.01%
polyethylene glycol; pH 6.0; osmotic pressure 290 mOs/kg) is
introduced into the intestinal loop and both ends of the loop are
ligated. Subsequently, the intestinal loop is immediately returned
to the abdominal cavity. An incandescent lamp is used to maintain
the body temperature. The solution inside the intestinal loop is
retrieved 20 minutes after its administration. The pH was measured
by pH-meter. The amount of medicaments are measured by HPLC.
[0070] In addition, the pH profile of substrates recognized by
PEPT1 can be obtained by measuring the uptake into oocytes under
various pH conditions once cRNA hPEPT1 is injected into X. laevis
oocytes. Alternatively, the pH profile can be measured using an
electrophysiological method by detecting the electric potential
difference generated upon adding substrates for peptide
transporters.
[0071] Specifically, the measurement can be conducted in reference
to the method described in "Expression Cloning of a Mammalian
Proton-Coupled Oligopeptide Transporter" by Fei, Y. J., Kanai, Y.,
Nussberger, S., Ganaphthy, V., Leibach, F. H., Romero, M. F.,
Singh, S. K., Boron, W. F., and Hediger, M. A., Nature 368 (1994):
563-566.
[0072] Generally, although the optimum pH for uptake of substrates
in the gastrointestinal tract varies according to the target
proton-coupled transporters and types of substrates, a pH profile
obtained according to the aforementioned methods shows the extent
of cellular uptake of substrates recognized by the proton-coupled
transporters under various pH conditions, thereby enabling the "pH
of the proton-coupled transporters optimum for cellular uptake of
substrates" to be determined. [0073] pH-Sensitive Polymers
[0074] pH-sensitive polymers herein refer to those that release
protons depending upon the pH of the specific site of a living body
(e.g., gastrointestinal tract), for example, polymers that dissolve
or swell by releasing protons under high pH conditions. By using a
specific amount of this pH-sensitive polymer in combination with a
substrate, the pH of the gastrointestinal tract (in particular,
sites adjacent to the surface of the brush border membranes of the
gastrointestinal tract) can be controlled to be optimum for
cellular uptake of a substrate recognized by the proton-coupled
transporter.
[0075] Specific examples include dried methacrylic acid copolymers,
methacrylic acid copolymers LD, methacrylic acid copolymers L,
methacrylic acid copolymers S, polyacrylic acids, maleic
acid/n-alkyl vinyl ether copolymers, hydroxypropylmethylcellulose
acetate succinates, hydroxypropylmethylcellulose phthalates, etc.
More specifically, examples are Eudragit L100-55 (Eudragit is a
registered trademark, same applies hereinbelow), Eudragit 30D-55,
Eudragit L100, Eudragit S100, Eudragit P-4135F, and the like. Those
commercially available and those prepared according to known
methods can be used as these pH-sensitive polymers.
[0076] Among these pH-sensitive polymers, preferably used in the
pharmaceutical preparation of the present invention are, for
example, Eudragit L100-55, Eudragit L100, Eudragit S100, Eudragit
P-4135F, and the like, and particularly preferable are Eudragit
L100-55 and Eudragit L100.
Pharmaceutical Preparations
[0077] The pharmaceutical preparation of the invention is
formulated by mixing, with a compound recognized by a
proton-coupled transporter, a pH-sensitive polymer in an amount
sufficient for imparting the pH optimum for cellular uptake of the
compound in the gastrointestinal tract based on the pH profile of
the compound. The phrase "in the gastrointestinal tract" as used
above refers, for example, to "in the small intestine". It refers
particularly to "in sites adjacent to the surface of the brush
border membranes of the gastrointestinal tract", and more
particularly to "at the surface of the brush border membranes of
small-intestinal epithelial cells where proton-coupled transporters
are expressed, and in locations adjacent thereto".
[0078] The amount of pH-sensitive polymer to be used can be
determined, for example, through experiments so as to obtain the
desired extent of substrate absorption. Specifically, the amount of
pH-sensitive polymer to obtain the desired extent of substrate
absorption can be determined by altering the amounts of
pH-sensitive polymer added to the substrate using the in situ
closed loop method or oral-administration in rats (see, for
example, Example 3).
[0079] The amount of pH-sensitive polymer used in the
pharmaceutical preparation of the invention, although it varies
according to the property of a substrate, may be, for example,
about 1 to about 1000 parts by weight, preferably about 50 to about
500 parts by weight, and more preferably about 100 to about 300
parts by weight, per part by weight of substrate. Alternatively,
the amount of pH-sensitive polymer may be about 5 to about 40 wt.
%, and preferably about 10 to about 20 wt. %, based on the weight
of the entire pharmaceutical preparation.
[0080] Preferable embodiments of the pharmaceutical preparation of
the present invention containing a compound recognized by a
proton-coupled transporter and a pH-sensitive polymer include
preparations containing a dipeptide and methacrylic acid copolymer,
preparations containing a .beta.-lactam antibiotic and methacrylic
acid copolymer, etc.
[0081] With regard to preparations containing a dipeptide and a
methacrylic acid copolymer, specific examples of the dipeptide are
glycylsarcosine, carnosine, lisinopril, etc. Specific examples of
the methacrylic acid copolymer are dried methacrylic acid
copolymers (e.g., Eudragit L100-55), methacrylic acid copolymers LD
(e.g., Eudragit 30D-55), methacrylic acid copolymers L (e.g.,
Eudragit L100), methacrylic acid copolymers S (e.g., Eudragit
S100), etc. An especially preferable embodiment include those
containing glycylsarcosine or carnosine, and Eudragit L100-55.
[0082] With regard to preparations containing a .beta.-lactam
antibiotic and a methacrylic acid copolymer, examples of the
.beta.-lactam antibiotic include penicillin antibiotics, cephem
antibiotics, and the like. Specific examples are amoxicillin,
ampicillin, ciclacillin, phenoxy-methylpenicillin, propicillin,
carfecillin, carbenicillin, bacampicillin, pivampicillin,
cefadroxil, cefixime, ceftibuten, cephaclor, cephalexin,
cephradine, SCE-100, cefatrizine, cephalothin, cefdinir,
loracarobef, FK089, latamoxef, pivcefalexine, cefazolin,
cefoperazone, cefoxitin, cefotiam, cefinetazole, etc. Specific
examples of the methacrylic acid copolymer are as described above.
An especially preferable embodiment includes those containing
cefadroxil, cefixime, or FK089, and Eudragit L100-55.
[0083] The pharmaceutical preparation of the invention comprises a
compound recognized by the aforementioned proton-coupled
transporter (substrate) and a specific amount of a pH-sensitive
polymer, and can be orally administered to mammals (especially
humans) as it is as a powdered medicine. The pharmaceutical
preparation can also be administered having been formulated
according to various methods. For example, it can be administered
as tablets, granules, capsules, suppositories, and enemas. The
pharmaceutical preparation in these forms can contain, as
necessary, excipients, disintegrants, lubricants, and various other
additives known in pharmaceutical production.
[0084] In particular, it is preferable to formulate an enteric,
sustained-release pharmaceutical preparation or the like that can
deliver the medicament and pH-sensitive polymer throughout the
gastrointestinal tract. Furthermore, the pharmaceutical preparation
can be formulated into a liquid form (such as solution, suspension,
syrup, and the like) containing the medicament and pH-sensitive
polymer, thereby, compared with conventional tablets, enabling more
thorough delivery of the medicament and pH-sensitive polymer, due
to its water content, throughout the gastrointestinal tract. The
pharmaceutical preparation can be formulated into these forms
according to known methods.
[0085] The pharmaceutical preparation of the invention enhances the
absorbability of a compound recognized by a proton-coupled
transporter in the gastrointestinal tract because the
gastrointestinal tract is conditioned by the pH-sensitive polymer
contained therein to the pH optimum for cellular uptake of the
compound. In particular, since the pharmaceutical preparation of
the invention contains a pH-sensitive polymer in an amount
sufficient to maintain the pH optimum for cellular uptake,
medicament (substrate) can be readily absorbed even in the lower
gastrointestinal tract (ileum and so on) where the amount of
protons is decreased, and thereby a decrease in transporting
ability of proton-coupled transporters is inhibited. Hence, the
pharmaceutical preparation of the invention, even when administered
orally, can provide a sufficient blood concentration of a
medicament and achieve high bioavailability. Incidentally, the
pH-sensitive polymer temporarily controls the pH of the
gastrointestinal tract and does not adversely affect the
gastrointestinal tract. The phrase "the pH-sensitive polymer
temporarily controls the pH" means that the pH of a site where a
substrate is absorbed into cells is impermanently controlled for an
amount of time necessary for the cellular absorption of the
substrate to complete.
BRIEF DESCRIPTION OF THE DRAWINGS
[0086] FIG. 1A is a graph showing the extent of cellular uptake of
dipeptides into Caco-2 cells under various pH conditions (pH
profile).
[0087] FIG. 1B is a graph showing the extent of cellular uptake of
.beta.-lactam antibiotics into Caco-2 cells under various pH
conditions (pH profile).
[0088] FIG. 2 is a graph showing the effect of an acidic polymer on
the pH of MES buffer.
[0089] FIG. 3 is graphs showing absorption and pH in the lower
small intestine of rats when a .beta.-lactam antibiotic (CDX or
CFIX) is used in combination with Eudragit L100-55.
[0090] FIG. 4 is a graph showing the time course of blood
concentration after orally administering CFIX and a polymer into
rats.
[0091] FIG. 5 is a graph showing the time course of CFIX blood
concentration after orally administering CFIX, Eudragit L100-55 and
CDX into rats.
[0092] FIG. 6 depicts an intestinal loop used in the in situ closed
loop method.
BEST MODE FOR CARRYING OUT THE INVENTION
[0093] Examples are given below to illustrate the invention in more
detail, but the scope of the invention is not limited to these
examples.
EXAMPLE 1
[0094] To investigate the effect of extracellular fluid on the
cellular uptake of dipeptides and .beta.-lactam antibiotics
transported by PEPT1, the cellular uptake of dipeptides, i.e.,
[.sup.14C]glycylsarcosine ([.sup.14C]GlySar) and
[.sup.3H]carnosine, and .beta.-lactam antibiotics, i.e., cefadroxil
(CDX), cefixime (CFIX), and FK089, was evaluated at pH 5.0 to 7.0
using gastrointestinal tract model cells (Caco-2 cells).
[0095] Cells cultured on 4-well plates were rinsed 3 times with 1
mL Hanks' balanced salt solution (HBSS: 0.952 mM CaCl.sub.2, 5.36
mM KCl, 0.441 mM KH.sub.2PO.sub.4, 0.812 mM MgSO.sub.4, 136.7 mM
NaCl, 0.385 mM Na.sub.2HPO.sub.4, 25 mM D-glucose, 10 mM HEPES; pH
7.4; osmotic pressure 315 mOs/kg) heated to 37.degree. C., and
uptake was initiated by adding 250 .mu.L HBSS containing medical
fluid. Uptake was terminated at a predetermined period of time by
washing the cells 3 times with 1 mL ice-cooled HBSS. After the
completion of uptake, 0.25 mL 5 N NaOH was added, and the cells
were agitated for 2 hours to solubilize, followed by neutralization
with 0.25 mL 5 N HCl. The medicaments contained in the solution
extracted from the cells were quantified by a liquid scintillation
counter or liquid chromatography (HPLC). Proteins contained in the
cells were quantified using a protein assay kit (Bio-Rad, Richmond,
Calif., USA) according to the Bradford assay (Bradford, M. M. "A
Rapid and Sensitive Method for the Quantitation of Microgram
Quantities of Protein Utilizing the Principle of Protein-Dye
Binding". Anal. Biochem. 72 (1976): 248-254).
[0096] FIGS. 1A and 1B show the effect of pH upon the uptake of the
aforementioned dipeptides and .beta.-lactam antibiotics into Caco-2
cells.
[0097] FIG. 1A shows the extent of uptake over 5 minutes, under
different pH conditions, of 10 .mu.M [.sup.14C]GlySar
(.circle-solid.) and 0.15 .mu.M [.sup.3H] carnosine
(.tangle-solidup.) into Caco-2 cells at a temperature of 37.degree.
C. Each plot represents the mean.+-.standard error of 3 to 4
experiments.
[0098] As shown in FIG. 1A, the uptake of [.sup.14C]GlySar is
clearly pH-dependent. The greatest uptake was observed between pH
5.0 and 6.0. On the other hand, FIG. 1A shows that the uptake of
[.sup.3H] carnosine, which is cationic in the weakly acidic region,
was significant between pH 6.0 and 7.0. That is, the results
demonstrated that the optimum pHs for [.sup.14C]GlySar and
[.sup.3H] carnosine uptake are different.
[0099] FIG. 1B shows the results of measuring the uptake of 2 mM
CFIX (.quadrature.), 2 mM FK089 (.largecircle.), and 2 mM CDX
(.DELTA.) over 15 minutes. Each plot represents the
mean.+-.standard error of 3 to 4 experiments.
[0100] As with the dipeptides, FIG. 1B shows that the uptake of
.beta.-lactam antibiotics into Caco-2 cells is significantly
pH-dependent, and that when the pH of the extracellular fluid is
decreased from 6.0 to 5.0 the cellular uptake of anionic
.beta.-lactam antibiotics CFIX and FK-089 was greatly enhanced. In
contrast, the optimum uptake of CDX, which is a zwitterionic
.beta.-lactam antibiotic at physiological pH, was observed at pH
6.0.
EXAMPLE 2
[0101] To investigate whether it is possible to control pH by
adding pH-sensitive polymers, the effect of such a polymer on the
pH of MES buffer was examined.
[0102] A methacrylic acid copolymer (Eudragit L100-55) was used as
a pH-sensitive polymer, and an aminoalkyl/methacrylate copolymer
(Eudragit RS PO) was used as a pH-insensitive polymer.
[0103] A polymer (methacrylic acid copolymer Eudragit L100-55 or,
of a pH-insensitive polymer, aminoalkyl/methacrylate copolymer
Eudragit RS PO) was added to MES buffer (pH 6.0). Subsequently, the
pH of the buffer was measured by a pH meter.
[0104] The pH of the buffer decreased as Eudragit L100-55 was added
(FIG. 2). In FIG. 2, plots (.circle-solid.) represent the pH of the
MES buffer containing Eudragit RS PO, and plots (.largecircle.)
represent the pH of the MES buffer containing Eudragit L100-55.
Compared with the pH of the buffer having no polymer content, pH
was decreased to about 3.0 when Eudragit L100-55 was added to a
proportion of 20%. In contrast, the use of Eudragit RS PO, which
has no proton-dissociating groups in its structure, did not result
in a significant decrease in pH.
EXAMPLE 3
[0105] To investigate whether gastrointestinal absorption in rats
of .beta.-lactam antibiotics under physiological conditions can be
improved by controlling the gastrointestinal pH, absorption of a
zwitterionic compound (CDX) and an anionic compound (CFIX) in the
presence and absence of a pH-sensitive polymer (Eudragit L100-55)
was examined using the in situ closed loop method (FIG. 6 shows a
diagram).
[0106] The oral composition of the invention was prepared by adding
a .beta.-lactam antibiotic (CDX or CFIX) to 10 mM MES buffer (pH
6.0) such that the buffer contained CDX in an amount of 1 mM or
CFIX in an amount of 0.5 mM, and further adding Eudragit L100-55 to
the buffer so that it contained in a proportion of 10 or 20 wt. %
based on the amount of the entire oral composition. A .beta.-lactam
antibiotic solution containing no Eudragit L100-55 was prepared as
a control.
[0107] These compositions were administered into the intestinal
loops prepared at the caecum junction of SD male rats (junction
between the terminal of the ileum and where the caecum starts) to a
distance of 14 cm toward the stomach. The solution remaining in the
intestinal loops was retrieved 20 minutes after administration. The
concentration of .beta.-lactam antibiotic in the retrieved solution
was measured by HPLC, and pH of the retrieved solution was measured
using a pH meter. Absorbability was evaluated according to the
decrease in the concentration of .beta.-lactam antibiotic in the
retrieved solution in comparison with the concentration thereof in
the solution administered.
[0108] As shown in FIG. 3A, absorption of CDX containing no
Eudragit L100-55 was about 40%. However, significant increase was
observed from the use of Eudragit L100-55 in a proportion of 20 wt.
%, resulting in CDX absorption of about 80%. Moreover,
gastrointestinal pH decreased as Eudragit L100-55 was added (FIG.
3B).
[0109] In contrast, CFIX was hardly absorbed by the rat ileum (FIG.
3C). However, as with CDX, the use of Eudragit L100-55 in a
proportion of 20 wt. % significantly improved CFIX absorption to
about 35%. The pH of the fluid in the gastrointestinal tract was
decreased by Eudragit L100-55 (FIG. 3D).
EXAMPLE 4
[0110] To investigate whether absorption of orally-administered
peptidergic compounds in rats is improved by controlling
gastrointestinal pH using pH-sensitive polymers, the time course of
the plasma concentration of CFIX was examined after orally
administering the peptidergic compound CFIX in combination with a
pH-sensitive polymer (Eudragit L100-55) or pH-insensitive polymer
(Eudragit RS PO).
[0111] The oral composition of the invention was prepared by adding
Eudragit L100-55 to an aqueous solution of CFIX (0.23 mg/mL) such
that the solution contained Eudragit L100-55 in a proportion of 5
wt. % based on the amount of the entire oral composition. A CFIX
solution containing no Eudragit L100-55 was prepared as a control.
These compositions were orally administered to SD male rats (body
weight: 190 to 220 g) fasted for an entire day and night such that
CFIX was given in a dose of 2.3 mg/kg. Blood was collected 15 to
480 minutes after administration, and the plasma concentration of
CFIX was measured by HPLC. Based on the plasma concentration
profile of CFIX thus obtained, the area under the plasma drug
concentration-time curve (AUC) and highest drug concentration
observed in plasma following administration of an extravascular
dose (Cmax) were obtained.
[0112] FIG. 4 shows the absorption profile of CFIX after orally
administering the composition into rats (CFIX: 2.3 mg/kg). Plots
(.largecircle.) represent absorption of CFIX in the absence of a
polymer, plots (.circle-solid.) represent absorption of CFIX in the
presence of Eudragit L100-55 (500 mg/kg), and plots (.quadrature.)
represent absorption of CFIX in the presence of Eudragit RS PO (500
mg/kg). Each plot represents the mean.+-.standard error of 5
experiments.
[0113] As shown in Table 1, when CFIX and Eudragit RS PO as a
pH-insensitive polymer were administered simultaneously, no
meaningful differences from the administration of CIFX alone were
observed in blood concentration-time curve area under the plasma
drug concentration-time curve (AUC), maximum plasma drug
concentration highest drug concentration observed in plasma
following administration of an extravascular dose (Cmax), or time
at which the highest drug concentration occurs following
administration of extravascular dose (Tmax). Also, no change was
observed in absorption of orally-administered CFIX.
[0114] However, when CFIX and pH-sensitive acidic Eudragit L100-55
were simultaneously administered, significant increases were
observed in AUC and Cmax compared with the control containing no
polymer, resulting in substantial increase in absorption of
orally-administered CFIX.
EXAMPLE 5
[0115] To investigate whether the effect of the pH-sensitive acidic
polymer enhancing CFIX absorption as shown in Example 4 was
mediated by a peptide transporter (PEPT1) expressed in
small-intestinal epithelial cells, the effect of CDX, which is a
substrate for PEPT1, upon CFIX absorption was examined after orally
administering CFIX and CDX simultaneously (FIG. 5 and Table 1).
[0116] The experimental procedure was as described in Example 4
except that CDX was simultaneously administered.
[0117] FIG. 5 depicts the influence of CDX on the oral
administration profile of CFIX after administering the composition
(CFIX: 2.3 mg/kg) to rats. Plots (.circle-solid.) represent
absorption of CFIX when Eudragit L100-55 (500 mg/kg) and 0 mM CDX
were used, plots (.tangle-solidup.) represent absoption of CFIX
when Eudragit L100-55 (500 mg/kg) and 2 mM CDX were used, and plots
(.box-solid.) represent absorption of CFIX when Eudragit L100-55
(500 mg/kg) and 10 mM CDX were used. Each plot represents the
mean.+-.standard error of 5 experiments.
[0118] As shown in FIG. 5 and Table 1, when Eudragit L100-55 and 2
mM CDX were administered simultaneously, although no significant
differences were observed in AUC of CFIX compared with the
administration of Eudragit L100-55 without CDX, Cmax was
significantly decreased. Moreover, when CDX was administered in an
amount of 10 mM, both AUC and Cmax of CFIX were significantly
decreased.
[0119] As demonstrated above, absorption performed by the peptide
transporter is considered to be involved in the improvement of CFIX
absorption attained by the use of Eudragit L100-55.
[0120] Table 1 shows the pharmacokinetic parameters calculated
based on the data points shown in FIGS. 4 and 5 representing the
time course of blood concentrations. TABLE-US-00001 TABLE 1
AUC.sub.0-8h Sample (.mu.g hr/mL) Cmax (.mu.g/mL) Tmax (hr) Control
10.81 .+-. 1.48 4.13 .+-. 0.50 0.72 .+-. 0.20 Eudragit L100-55
.sup. 27.60 .+-. 2.39.sup.a 11.52 .+-. 1.86.sup.a.sup. 1.20 .+-.
0.20 Eudragit L100-55 + 24.24 .+-. 4.20 .sup. 6.39 .+-. 0.88.sup.b
1.00 .+-. 0.00 CDX 2 mM Eudragit L100-55 + .sup. 11.52 .+-.
0.99.sup.b .sup. 3.40 .+-. 0.60.sup.b 1.43 .+-. 0.20 CDX 10 mM
Eudragit RS PO 8.83 .+-. 0.28 3.39 .+-. 0.16 1.00 .+-. 0.00 Each
data represents the mean .+-. S.E.M. of three experiments at least.
.sup.aSignificantly different from the corresponding control value
at p < 0.05. .sup.bSignificantly different from the
corresponding Eudragit L100-55 values at p < 0.05.
[0121] All the references cited in this specification are
incorporated herein by reference.
EFFECTS OF THE INVENTION
[0122] The pharmaceutical preparation of the present invention has
been completed based on the finding that cellular uptake of a
substrate is enhanced most at the optimum pH for a proton-coupled
transporter. The pharmaceutical preparation of the invention,
therefore, is prepared, in view of the optimum pH of a
proton-coupled transporter for cellular uptake of a substrate, by
adding a pH-sensitive polymer in an amount sufficient for attaining
such pH.
[0123] Hence, the pharmaceutical preparation of the invention
dramatically improves absorption of pharmaceutical compounds in the
gastrointestinal tract and achieves, through oral administration or
like method, high blood concentration from which sufficient
remedial effects are expected.
[0124] Furthermore, the pharmaceutical preparation imparts high
absorbability throughout the entire gastrointestinal tract even to
compounds recognized by proton-coupled transporters that have been
known to be of poor absorbability.
[0125] Thus, the pharmaceutical preparation of the invention has a
pharmaceutically remarkable property that it can effectively
improve the remedial effects of oral administrations or like
methods with low doses.
* * * * *