CA1045975A - Enzyme degradable medicament carriers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A controlled release insert for a living eye con-sisting of a biologically effective form of pilocarpine and a biologically inert biodegradable carrier consisting essen-tially of poly[N-acetyl-6-0-(carboxymethyl)-D-glucosamine]
gives effective treatment to the human eye for prolonged periods. Other medicaments and other enzymatically degrada-ble forms of poly(N-acetyl-D-glucosamine) may be used for rate controlled release in the eye and other areas.

Description

25,16n '1~4597~i ;
BACKGROUND OF THE INVEN~ION
~ his invention relates to the controlled release of drugs. The time of release of medicament~ or drugs can be in part co~trolled by incorporating the drugs i~ a matrix of a~
enzymaticall~ degradable form of polg(N-acetyl-D-glucosami~e) ~o that said form i~ slowly enzymatically degraded over a period of time by body fluids and the drug i9 released into the body fluids at the time of use for a longer period than ~he drug would be released without the matrix carrier. ~;
~e prior art shows many efforts over a long period by many individuals to alter the rate of release of drugs.
Where it is considered that drugs may be administered to many areas and for man~ different conditions and that various drugs have different solubilities in both water and oil, and the period for desired administration may varg from almost i~-stantly to a long period of up to and including years, it càn be ~een that there is a wide range of medicaments and a wide range of conditions to be controlled.
, DESCRIPTIO ~
U. S. Patent 2,552,027, Bird and Rochow, May 8, 1951, CAS~ING GELATIN ~AB~E~S, discloses the incorporation of medica-ments~ particularly vitami~s, into a gelatin-glycerine matrix, which are "particularly useful for the administration of vita-~ ins or other pharmaceutical materials which should be released25 in the stomach or digestive tract at comparativel~ slow rates."
In U. S~ Patent 3,604,417, Stolzenberg and Linken-~; heimer~ September 14, 1971, OSMOTIC FLUID RESERVOIR ~OR OS-MOTICA3LY AC~IVA~D IO~G-~E~M CO~TINUOUS INJ~CTOR DENICE osmo-tic pressure i8 used to propel a piston system so that a drug i8 810wly injected.
Many coating systems have been used on tablets for enterio release in which various capsules have been coated -1- ,~ `

25,160 ~5~75 either a~ a single tablet or by coating particles in the tab-lets or capsules so that drugs are released into the stomach or intestine at a controlled rate and for a longer period tha would result from the administration Or the medicam~nt without such coatings.
U. S. Pate~t 3,739,773, Schmitt and Polistina, June 19, 1973, PO~YG~YCO~IC ACID PROSTH~IC DEVIa~S, in Col-umn 6~ line 53, refers to polyglycolic acid in combination with other products as slowly digestible drug release devices.
This patent in Column 7, lines 47 and following, mentions that d~es, antibiotics, antiseptics, anesthetics, and other ma-terials may be present in polygl~colic acid devices. ~his la~t language also appears in Column 3, line 48 and following o~ U. S. Patent 3,297,033, Schmitt and Polistina, January 10, 1967, SURGIC~L SU~URES.
U. S. Patent 3~435,008, Schmitt, Epstein a~d Poli-~tina, ~arch 25, 1969, METHOD ~OR PREPARATIO~ 0~ ISOMERI-CA~LY PURE ~-G~YCO~IDE AND PO~YMERIZA~IO~ M~OD ~OR G~YCOLID~
COMPOSI~ION~ ~MPIOYI~G PARTIAL HYDRO~YZATE 0~ SAID ~-G~YCO~ID~
in Column 7, line 19 and following, discloses glycolide poly-mers as coatings ror medicaments to alter their digesti~e characteristics.
U. S. Serial ~o. 179,129~ available through conven-tion documents in the file o~ Netherlands 7,212,272, in Ex-ample 14 discloses a bioerodible ocular insert containing -~
pilocarpine using a matrix of polyglycolic acid. Pilocarpi~e i~ mixed with polyvinyl alcohol and used as a core between two sheets of polyglycolic acid. tsee page 112). Page 60 discloses polyester~ of lactic a~d glycolic acid as a carrier.
Page 739 line 11, mentions "chitin" among other polysaccha-rides and plant hydrocolloids. Presumabl~, the reference i~
to the naturall~ occurring form of chitin. ~laim 5 i~ drawn

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~ `^ ~

~45~7S ~;
to bioerodibility by e~zymatic cleavage. Claim 14 is drawn to cross-linked gelatin. Claim 50 i9 drawn to polylactic or polyglycolic release rate controlling materials.
Sterile peanut oil and similar materials have been used as a repository for penicillin for some time. The peni-cillin is slo~ly released from the repository. Unfortunately, the peanut oil or beeswax remains behind and is apt to form a sterile abscess rather than be absorbed by tissues.
C~rboxymethylchitin is disclosed in Carbohyd. Res.
7, 483-485 (1968), Ralph Trujlllo.
This article mentions the hydrolysis of both chitin and carboxymethylchitin by lysozyme.
Chitin has been estimated to be the second most abundant polysaccharide in nature with a synthesis in the neighborhood of a billion tons a year by marine organisms.
See Chitin, N.V. Tracey, Reviews of Pure and Applied Chemi-stry, Royal Australian Chemical Institute, Vol. 7, No. 1, March 1957, Pages 1-14.
` The above patents and articles describe chitin, its properties and derivatives.
Although it is well recognized that systems for tha controlled release o~ drugs are very much in demand, the wide range of requirements is such that useful contributions are still being sought and major efforts are being made by many research organiæations to improve drug delivery device$.
SUMMARY OF THE INVENTION
- ~ .
It has now been found that enzymatically degrada-ble forms of poly(N-acetyl-D-glucosamine) sometimes herein abbreviated as PAG, are comparatively storage stable and re-sistent to hydrolytic degradation so that medicaments may be incorporated and stored in a matrix of such biodegradable form ~4 ~'` ~ ' ' .
, . ~
, .

g7S ,~
PAG, and the medicament then released in the tissue of liv-ing mammals by the enzymatic degradation of the biodeqrada~
ble form of PAG. The enzyme lysozyme is particularly effec-tive in the enzymatic degradation of the biodegradable forms of PAG. Various forms of PAG may have different degradation rates, and the degradation rate may vary with the location of the drug release device.
Usually it is desired that the drug release device be mechanically acceptable at a location of use. For instan-ce, an ocular insert may be designed to be placed adjacent tothe eyeball inside the eyelid, in the cul-de-sac of the con-junctiva between the schlera of the eyeball and the lid. An insert needs to be soft so that it will cause a minimum o irritation to the eyeball and the degradation products are preferably such that they may be washed away by the flow of tears without the necessity for removal of the device after its drug content has been delivered. For other locations, `~
such as implantation beneath the surface of the skin or in-sertion in the utuerus as an anti-fertility device, the like- ~ ;
lihood of irritation from the mechanical aspects of the de-vice are much less. `
Because the requirements ~or use in the eye are `
! among the more rigorous, the present device will be described particularly in conjunction with the use in the eye although it is to be understood that the device in its many forms may be used in other locations.
N-acetyl-D-glucosamine has the formula: ~

~ `

~ .

~5,160 ,. ..
.. .

;^ 6 ~: 1~* ~

~ ~ 1 or NHCCH~

'~ 10 HO 4\~

;~s~ HCC~ ~H
~ O
Groups below the plane of the paper are shown b~ a dotted bond.
~i' Pol~ acet~l-DLglucosamine~ has ascribed to it the formula (ring h~drogens omitted for clarit~) r, ' . .

6 ~2 ~ ~IO~ I C
~ ~5 ~.~"~
HAC ~ OH

Poly(~-acetyl-D~glucosamine) is a ma~or component of ',l naturally occurring chitin. ~he naturally occurring material has not only the poly(~-acetyl-D~glucosamine) but also inor-ganic salts thought to be forms of calcium carbonate and proteinaceous material, the composition of which is not pre-

3 sently known. The term "chltin" is used herein to refer to I the various naturally occurring forms of~chitin including the protein and inorganic carbonate components. ~he term 1l i ~ '. , ~ ' I
~ ~ . . .. ..

l --; 25,160 1045~75 "purified chitin" i9 used to refer to chitin after purifica-tion to remove calcium carbonate and other inorganic salts and various proteins which may be present and is essentially poly(N-acetyl-D~glucosamine). Some confusion exist-~ in the ; 5 literature in that the name chitin is used as a name ~or poly(N-acetyl-D~glucosamine~ without specirging whether it is a naturally occurring material containing inorganic salts ~ and proteins or whether the term is intended to designate purified poly(~-acetyl-D-glucosamine) without specifying the .~ 10 degree of purity or the character o~ the impurities present.
~he term "enzymatically degradable form of poly(~--acetyl-D-glucosamine)" refers both to the purified poly(N--acet~l-D~glucosamine) from chitin itself as well as the carboxymethyl, hydroxyethyl, and O-ethyl derivatives, etc.
~he carboxymethyl derivative, properly called `~
poly~N-acetyl-6-0-(carboxgmeth~l)-D~glucosamine] has the `~
:J~ :
I formula ~
~:

~I HO ;
' 20 Q~ oc~ COOH ~ ~ ~c ;' "0~ = ~"`0/
~ ~ ~ELAc C~ OC~ COOH

.i ~he hydroxyethyl derivative, properly called poly~N-acetyl-6-0-(2'-hydroxyethyl)-DLglucosamine] has the formula ',,s~

.', :

i ' ~ .

25,160 "

~ ~04597S

, .
OC~ CH~ 0~ ~0, NHAc ~ ~
o~ o~' ~-Ac 4 C~2 C~2 CH~ S)E

~he O-ethyl derivative, properly called poly-~: rN-acetyl-6-O~(ethyl)-DLglucosami~e~ has the formula ~' 10 .` CH~OC~ C~ HO ~ c ~ 15 XO ~ c CE~OC~ CH3 j~ ' III

~he above forms are sometimes hereinafter designated ~ by the Roman Numeral below the ~ormula.
`~ Other similar derivatives which are enz~matically : 2 degradable, particularly by lysozyme, are included within the eneric term "enzgmatically degradable form o~ poly(~-acetyl-_~Lglucosamine)~.
~ ~¢ause o~ the nature of the polgmers~ carboxymethyla-:~ tion, hydroxyethylation, or ethylation may not be 100%, and may in part o¢cur on the 3-hydroxyl. Unle~s otherwise speci-` fied~ under or over-substitution Or the pol~[N-acet~1-6-0-(carbox~methyl~-D-glucosamine] is to be included as a biode-: ~ gradable form of PAG. ~he solubilit~ in a specified solvent :~ is one test of the degree of substitution. ~or example, the O-ethyl derivative is water ~oluble when the eth~l group to glucosamine ratio is about 1 and organic soluble when the degree of ~ubstitution is greater than 1.
,~
~:~ : ~7 I

; . ., .;

~ 5~75 The term "drug" is used to refer to a substance other than a food intencled to affect the structure or function of the body of man or other animal. The term is somewhat broad~
er than "medicine" in that the term "medicine" is sometimes considered to be restricted to an agent which is administered to affect or control a pathogenic condition. The broader term "drug" here is also used to include steroids and other fertil- -~,; ity controlling agents which may be incorporated in an intra~
uterine contraceptive device or other materials which may he -., , ~
included to affect the fertility of females or males either ~; as an intrauterine device or subcutaneously.
$~ The term "dispensing" is used to designate a method of administering a drug to man or other animal and includes the release of the drug to a desired location. This would in-clude the eye, gastrointestinal tract (alimentary), intrauter-inely, intramuscularly, subcutaneously, or into the mucosa of the nose, mouth (sublingual), or rectum, etc. The release over a prolonged period of time designates any decrease in the release rate of the drug over that which would be expected if . ':
. ; 20 the drug were administered alone and would include from the matter of a few minutes as, for example, in an ocular insert containing pilocarpine to a duration of six months to a year which might be desired for the administration of a steroid in ,l an intrauterine contraceptice device. For some conditions, even a longer period o administration, such as the lifetime ~ of the patient, could be desired but usually a period of a '~ very few hours up to about six months includes the medically preferred range. ;;
Because the enzymatically degradable form of poly-~; 30 (N-acetyl-D-glucosamine) is a solld which can be removed, a long-acting repository pellet for insertion beneath the skin ~i~ is quite practical as if for any medical reason it is desired ~4~75 to discontin~e administration o~ the drug, the insert with the remaining drug charge may be removed simply by excision.
The term "enzymatically degradable" refers to a form of poly(N-acetyl D-glucosamine) or its derivatives which is broken down into body fluid soluble components and which are washed out as in tears, or transported elsewhere by tears, or other body fluid, and later degraded further or metaboliæed by the body or excreted by the body. The problem of retention by the body or disposal of the residual matrix is minimal or non-existent.
While other enzymes may also affect the enzymatic degradation of the poly(N-acetyl-D-glucosamine) matrix, the enzyme which is most widely distributed in the body and here very effective is lysozyme. Lysozyme occurs in practically all of the body fluids, particularly the tears, and effective-ly breaks down the polymer chain to water soluble or disposa-ble components.
Chitosan, which is a common name for the deacylated form of poly(N-acetyl-D-glucosamine), and which is poly~D--glucosamine) is not enzymatically degradable by lysozyme.
By contrast, the present enzymatically degradable forms of poly(N-acetyl-D-glucosamine) are not readily hydro-lyzed by water. For instance, I in a phosphate buffer at PH
7.2 at 37C for 24 hours is not hydrolyzed whereas under the same time and temperature in the presence of lysozyme hydroly-sis occurs.
It is highly advantageous to have the degradation of the enzymaticalLy degradable form of poly(N-acetyl-D-glucosa-mine) occur only by the action of an enzyme as the resistance to hydrolytic degradation markedly reduces problems of manu-facture and storage in the presence of ambient moisture, and ensure a steady smooth surface erosion rather than a _ 9 _ 25,160 ~ )4597S
fragmentation process commonl~ experienced b~ pol~mers which are hydrolyæ sd by smal 1 mol ecul e s .
Any of the drug~ used to treat ~he eye and surround-ing tissues can be incorporated with the enz~maticall~ de-5 gradable form of PAG of this invention. Also, it i~ practi-cal to use the e~e and surrounding tissues as a point of entr~
- for s~stemic drugs that enter circulation in the blood stream and produce a phaxmacolo~ical response at a site remote from the point of application o~ drug and the enz~matically de-gradable ~orm of PAG matrix. ~hus, drugs which will passthrough the e~e or the tissue surrounding the eye to the blood-stream, but which are not used in therapy of the eye itself, can be incorporated in the enzymatically degradable PAG matrix.
~uitable drugs for use in therap~ of the eye with the present insert include, without limitation: Anti-in-~ectives: such as antibiotics, including tetracycline, chlor-tetracycline, bacitracin, neomycin, polymyxin, gramicidin, oxgtetrac~cline, chloramphenicol, and erythromycin; sulfona-mides, including sulfacetamide, sulfamethazole, and sulfisox-azole; antivirals5 including idoxuridine; and other anti--infectives including nitrofurazons and sodium propionate;
Antiallergenics such as antazoline, methapyrilene, chlor-pheniramine, p~rilamine and prophenpyridamine; Anti-inflamma-tories such as h~drocortisone, hydrocortisone acetate, dexa-methasone, triamcinolone, medr~sone, prednisolone, predniso-lone 21-phosphate and prednisolone acetate. Decongestants such as phen~lephrine, naphazoline, and tetrahydrazoline.
Miotics and anticholinesterases such as pilocarpine, eserine salic~late, carbachol, disopropyl fluorophosphate9 phospholine iodide, and demecarium bromide; matropinej scopolamine, tropi-camide, eucatropine, and hydroxyamphetamine and Sypathomine tics ~uch as epinephrine. Drugs can be in various ~orms, , 25,160 ~ 0~5~7~
~uch as unchanged molecule~, components o~ molecular com-plexes, or nonirritating, pharmacologically acceptable salts9 such as hydrochloride, hydrobromide, sulfate, phosphate, nitrate~ borate, acetate, maleate, tartrate, salic~late, etc.
Furthermore, simple derivatives of the drugs (such as ethers, esters~ amides, etc.) which have desirable retention and re-lease characterics but which are easily hydrolyzed by body pH, enzymes, etc. can be employed. The amount of drug in-corporated in the ocular insert varies widely, depending on the particular drug, the desired therapeutic effect, and the time span for which the ocular insert will be used. ~ince the ocular insert is intended to provide the complete dosage regime for eye therapy for but a particular time span, such ` as 24 hours, there is no critical upper ~imit on the amount ~ drug incorporated in the device. ~he lower limit will depend on the activity of the drug and its capability of being released from the device. ~hus, it is not practical to de~ine a range for the therapeutically effecti~e amount of drug in-corporated into the device. However, typically, from 1 micro-gram to 1 milligram of drug is incorporated in each insert.
In each case~ the pol~meric material used to formthe ocular insert is chosen for its compatibility with a parti-¢ular drug and its capability of releasing that drug at an appropriate rate over a prolonged period of time. Specific, but nonlimiting, examples of combinations of drugs and poly-mers for use in forming the ocular insert include: poly-~N-acetyl-6-0-(carboxymethyl)-~gluco~amine] and epinephrine;
poly~-acetyl-6-0-(carboxymethyl)-D~glucosamineJ and mixture of pilocarpine hydrochloride and epiniphrine; poly[N-acetyl--6-0-(2'-hydroxyethyl)-D-glucosamine] and acetRæolamide;
poly[N-acetyl-6-0-(ethyl)-D~glucosamine] a~d phospholine iodide; poly[N-acetyl-6-0-(carboxymethyl)-DLglucosamine] and .. .

, .. . .
....
. .. . . .
.

25, 16~ -~3L04S~75 triamcinolone~ or in general any of the drugs listed above and the enzymatically de~radable form Or poly(N-acetyl-D--glucosamine), including degrees of substitution greater or les~ than 1, and related derivatives such as other lower alkyl derivatives instead of poly[~-acet~1-6-0-(ethyl)-D--glucosamine], other carboxyalkyl derivatives, and their esters and salts, hydroxyalkyl derivatives, etc.
~he degradation rate of the enzymatically degradable form of poly~-acetyl-D-glucosamine) can be lowered by cross-linking, if a slower release rate is preferred.
The ocular insert can be fabric~ted in any convenient shape for comfortable retention in the cul-de-sac. It is im-portant, however, that the device have no sharp, jagged, or rough edges which can irritate the sensiti~e tissues of the eye. ~hus, the marginal outline of the ocular insert can be ellipsoidal, bean-shaped, rectangular, etc. In cross section, it can be concavo-convex, rectangular, etc. As the ocular insert is flexible and, in use, will assume essentially the configuration of the scleral curvature, the original shape of the device is not of controlling importance. Dimensions of `
the device can vary widely. ~he lower limit on the size o~
the device is governed by the amount of the particular drug to be applied to the eye and surrounding tissues to elicit the desired pharmacological response, as well as by the smallest sized device which conveniently can be inserted and removed from the eye. ~he upper limit on the size of the device is governed by the limited space within the cul-de-sac that conveniently and comfortably can be filled with an ocular insert. ~ypically, the ocular insert is 4 to 20 millimeters in leng~h, 1 to 12 millimeters in width, and 0.1 to 1 milli-~eter in thickness. Pre~erably, it i8 ellipsoidal in shape ~-~
and about 6 x 4 x 0.5 millimeters in size. ; ~
: , ;12~ ~
. . .

25,160 lV4~597 ~
While particularly convenient for an insert in the eye1 the matrix containing the drug of the present invention can include other drugs for other areas. ~or instance, if the drug i9 to be taken orally, a tablet of a size and shape adapted to being swallowed i8 preferred. If it is to be placed subcutaneously, a tablet or rod such that it may be placed under the skin in an appropriate location is selected.
~he amount of drug and the time over which it is to be dis-pensed are controlling i~ the choice of size of the implant.
While the drug may be combined with the enz~mati-cally degradable form of PAG matrix in any co~venient way, it i8 particularly convenient to dissolve both in a common sol-vent which permits casting of the enz~matically degradable ~orm o~ P~G as a matrix containing the drug to be dispersed therein.
Poly(N-acetyl-DLglucosàmine~ is reported to be in-~oluble in all solvents except 88% phosphoric acid which badl~
degrades the polymer. Unexpectedly, it has ~ow been found 3 that hexafluoroisopropanol ~XIPA) and hexafluoroacetone ses-~uihydrate (HFAS) are solvents for the polymer. These are extremel~ powerful solvents~ and so much so that care must be used in selecting drugs which are compatible with such solvents to form solutions ~or casting.
PolyCN-acetyl-6-0-(carboxymethyl~-DLglucosamine], I, poly~-acetyl-6-0-(2'-hydroxyethyl~-D-glucosamine], II, and poly~N-acetyl-6-0-(ethyl)-D~glucosamine]~ III, are pre~erred I because of cosolubility with many drugs in common solvents, ¦ including water. Non~toxic solve~ts are preferred.
I and II are water soluble at the ~% level, and III is water soluble at the 5% level if the degree of substi-tution is not more than about 1, and organic solvent soluble if more than about 1. Organic solvents ma~ be used such as ~,..................................................................... .
-,-- - . ., 1 , : . '. ' ' . . : , .

25,160 :10~5975 alcohol~, chloro~orm, benzene, toluene, mixtures of benzene and toluene with alcohols and ketones.
Pilocarpine or other drugs can be incorporated into matrices of these en~ymatically degradable forms of PAG by hydrogen bonding, covalent bonding, ionic bonding or simple entrapment. The matrices themselves can be variably cross-linked with a variety of physical and chemical agents. The~
can be sterilized and when hydrated become quite pliable, while retaining adeguate strength to resist manipulation.
Present day therapy of topical drug application consists of drops and ointments. There are several defici-encies associated with these methods of delivery ~ it is impossible to achieve 24 hour control of the disease (2) it i8 wasteful with respect to the amount of drug used (3~ some people show strong sensitivity to cholinergic and adrenergiG
drop~ (4) many patients fail to apply the medioation as di-rected resulting in poor control of the disease (5) side ef-fects result from the drug passi~g through the lachrymal duct into the circulatory system. The herein described invention eliminates these problems and provides a means of releasing medication into the tear films in therapeutic levels con-; tinuously. ~he device is biodegradable and, hence, it is not ~ecessary to remove from the eye and also capable of deliver-ing large dosages giving it broad drug applicability. ~his in-vention constitutes a more efficient means of drug delivery that prolongs and enhance~ the drug effect.
As the scope of this invention is broad, it is ~1-lustrated b~ the following typical examples in which tempera-tures are centigrade, and parts are by weight unless clearl~
, .
I 30 otherwise specified.
,. .

:. . , ' . , - ,' ~ ' ;

25,160 ~~

i0 ~ ~9~5 ~ .
Purification 0r Chitin _ A commercial grade of chitin (Cal-Biochemicals) was finely ground in a ball mill overnight to pass a 6 mm screen and be retained by a 1 mm screen. 149 g. of thîs fi~ely ground material was decalcified by extracting with 825 ml. of 2N HCl at 4C for 48 hours, in a flask stirred with a magnetic stirrer. The material was collected by ¢entrifugation and washed repea~edly with water until neutral.
~he ash content was 0.4-0.5%. ~he decalcified chitin was then stirred at room temperature with 1500 ml. of 90% formic acid overnight. The mixture was centrifuged and the residue re-peatedly washed with water. The washed chitin was then sus-pended in 2 1. of 10%NaOH solution and heated at 90-100C.
for 2.5 hours. he solution was filtered, the cake washed with water until neutral, washed several times with absolute ethanol and ether, and dried at 40C. under reduced pressure;
I yield 66 g. of poly(N-acetyl-D-glucosamine). Infrared spec-¦; trum (EBr pellet) shows bands at 3500 cm~l (S), 2900 (W), 1 20 1652 (S), 1619 (S~, 1550 (S), 1~70 (S), 1300 (M), 1070 (Broad).
(S is ~trong, M is medium, W is weak).
E~ample II
Poly~N-acetyl-6-0-~carboxymethyl~-D-glucos~mine]
15 g. 0r the poly(~-acetyl-D-glucosamine) from Ex-ample 1 was swollen with 100 ml. of dimethylsulfoxide (DMS0).
To this highly swollen suspension was added 400 ml. of 2-pro-panol and the mixture stirred vigorously under nitrogen while 40 mlO of 300io agueous NaOH was added over an interval of 30 minutes at room temperatureO After stirring for an additional hour, 18 g. of chloracetic acid dissolved in 40 ml. of water was added dropwise over a 30 minute period~ The mixture was then heated at 55C. for 24 hours. The mixture was decanted '` ' - . : . . . : . .
,, , ~5~160 ~

10~975 and to the residue was added 100 ml. of 70~ methanol. ~he suspension was then neutralized with 5 ml. of 90% acetic acid~
m e mixture was filtered, washed with 70% methanol, absolute methanol and dried at 40C. in vacuo Yield 24 g. of poly-~N-acetyl-6-0-(carboxymethyl)-D~glucosamine]~ I. Infrared (~Br pellet) shows bands at ~00 cm 1. (S), 2900 ~M), 1600 Broad (S), 1400 (M), 1320 (M), 1100 Broad (S) D A sample was titrated and shown to have 4.03 meg acid/g indicating 100%
o~ the repeating mers were carboxylated. ~ilms easily re-moYed from glass were cast from water solution and shown to be transparent, flexible and tough.
Example III
Preparation of pol~(D~ _samine3 ~ ;
,, A procedure similar to that described by P. Brous-signoc, Chemie and Industrie, 99 (9) (68~, 1243 was used. ~o a solution of 180 g. of 96~/o ethanol and 180 g. ethylene gl~col was added 360 g. ~OE with stirring. ~o this solution was then added 54 g. of poly(~-acetyl-DLglucosamine) (purified I~ Chitin) from ~xample I and the mixture heated at 120C. for ¦ 20 6 hours. After cooling an equal volume of water was added to the mixture. ~he mix~ure was filtered and washed several times with water until neutral, then twice with acetone, and ~ ;
dried in vaauo. Yield 42~6 g. of poly(DLglucosamine)~ some- ;
times called chitosan. Infrared spectrum (EBr pellet) showed bands at 3450 cm 1~ (S), 2900 (M), 1620 (S~, 1600 (S), 1370 ~tBroad (S)~; 1050 ~Broad (S)]. Upon potentiometric titration of the sample 81.4~ of the mers were found to be deacylated.
~ he prod~ct is soluble in 3% acetic acid and forms clear, T~ flexible~ tough films from this solution. It is not enzymati-cslly biod-gradsble by lysoz~me.

f~

.
:` .` : , , 25,160 l~S975 ~ .
D~Glucosamine~Pilocarpine Film ~ o 5 ml. of 3% acetic acid wa~ added 0.25 g. of p~ly(D-glucosamine~ from Example III~ ~o the solution thus formed was then added 50 mg. pilocarpine free base and 100 ul of tritiated pilocarpine, and the mixture was cast a a film ~40 mil wet thickness) on glass. This film was crosslinked by dipping the film in 37% formaldehyde solution for 5 hours.
æhis film showed zero order release over a period of 3 days at which time it was still releasing pilocarpine at a zero order rate. About 70 percent of the pilocarpine remained in the film matrix after 3 days. ~he use of tritiated pilocarpine permits the use of a liquid scintillation coun~er to monitor the j release rate accurately and conveniently. ~adiological hazards are associated with such tritiated material in the treatment of human subjects so experimental animals are preferred to I ~tudy release rates.
Il ~e~Z
.
Pol~[N-Acet~1-6-0-(aarboxymeth~l)-DLGlucosa ine]/Pilocarpine Fil ~o a 5% solution of poly~-acet~1-6-0-carboxymeth~l)--DLglucosamine] (0.95 g.) in water was added 50 mg. of pilo-carpine nitrabe and 100 ul Or tritia~ed pilocarpine. A film 40 mils thi¢k was cast on a glass ~late and allowed to dry.
~he film was crosslinked by dipping into 10% alum for 5 hoursO
Release of pilocarpine ~rom this ~ilm in an agueous solution approximating human tears is essentially first order, with 90% of the pilocarpine being released within about 5 hours.
~xample VI
Pol~(N-Acetyl-D-Glucosamine) Matrix Membranes of poly(N-acetyl-D-glucosamine~ were pre-; pared by dissolving poly(~-acetyl-DLglucosamine) in each of hexafluoroacetone sesguihydrate (l.4h solution) and hexa-25~

104~975 fluoroisopropanol (2% solution~. The films were tough, tran~-parent, non-tacky, flexible and were guite pliable when hy~
drated yet retained adequate strength to resist manipulation.
~he membranes showed no hydrolysis after exposure to water ~or 5 days~ In the presence of l~sozyme, however7 the films were degraded slowly. ~he films eroded release any drug in the .:
film slowly.

~xample VII
Biodegradability of Pol~[~-Acetyl-6-0-(Carboxymethyl~-D
~Glucosamine~
After 24 hours incubation at 37C. in phosphate , , buffer pH 7~2 containing 1500 units/ml of lysozyme, polytN- ~
-acetyl-6-0-(carboxymethyl)-D~glucosamine~ was hydrol~zed to ,~,, oligomers as deter~ined by Gel Permeation Chromatography. A
control containing no enzyme was not hydrolyzed under the same condition~.
Example VIII
~1 In Vivo Results Using Poly~N-~cet~1-6-0-(Carboxymeth~l)-D-l ,-Glucosamine]/Pilocar~ine ~ 20 Membranes of poly[~-acet~1-6-0 (carboxymethyl)-D- ~, ,~ -glucosamine] were evaluated in vivo for sustained pharmacolo- -gical e~fect and eye irritation. I~ the right eye of each of .
three rabbits was placed a 1 mm x 10 mm film strip of pol~N--acetyl-6-0-(carboxymethyl)-DLgluco~amine~ (0.25 g. polytN--acetyl-6-0-(carboxymethyl)-D~glucosamine]/0.64 g. pilocarpine~
I Within 15 minutes after implantation of the film strip a sub-stantial lowering in pupillary constriction was observed and ;' lasted approximately,6 hours. ~he membranes were well tolerated ~' and slowly eroded in the eye. Such a prolonged effect in rabbits can be extrapolated to a 24 hour effect in humans since the rabbit metabolizes pilocarpine more rapidly than a human.

,~ .
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25~160 ~L~)4S975 Pol~rN-Acet~1-6-0-(2 ' -Hydrox~eth~l ~-D Glucosamine]
Inko a screw cap bottle was placed 13.6 Es. 0~ puri-fied PAG milled so that it passes a 1 mm. sieve. ~o the bottle was added 200 ml. of cold tO-5C. ) aqueous 43% NaOH
a~d the contents stirred for 2 hours u~der nitrogen and then held at 0-5C. for lO hours. ~he swollen alkali derivative was then sgueezed to 3 times its original weight in a sintered glass ~unnel, disintegrated and frozen at -20a. under nitro-gen for l hour and then thawed at room temperature for l hour.
~he freeze-thaw cycle was repeated 3 times. ~o the alkali ~
derivative was then added 120 ml. of dimethylsulfoxide (DMS0~ -and the slurry added immediately to a stirred autoclave. ~he autoclave was purged several times with nitrogen and 53.2 ml.
of ethylene oxide was added (16 equivalents/equivalent of PAG).
~he mixture was held at 50CC. for 18 hours. ~he solution was then carefully neutralized with glacial acetic acid, dialyzed ~nd then lyophilized.
.i~
~he hydroxyethyl derivative can be further purified b~ precipitatin~ the polymer from aqueous solution with acetone.
i ¦
A fre~hly precipitated 3ample of poly~N-acetyl-6-0-(2'-hydroxy-ethyl)-D~glucosamine] readily dissolved in water, 5% aqueous ~odium hydroxide, and 3% acetic acid and is precipitated from ~ these solutions by acetone. Samples analyzed for C, H and yj 25 showed the composition to be one in which 1.5 hydroxyethyl groups had been substituted per glucosamine residue.
., .
Example X
Pol~EN-Acet~l-6-o-(Eth~ DLGlucosamine]
~he procedure of ~ample IX was followed except 75 ml.
3 of ethylchloride was added i~stead of ethylene oxide and the reaction held at 50C. for 15 hour~. A water soluble deriva-tive is obtained.
~, 9_ ,. . ~.
55~75 ~o obtain an organic soluble derivative, the ethyl-chloride was mixed with benzene (75% of the amount Or ethyl-chloride). The reaction time was 10 hours and the temperature was controlled as follows: 1 hour heating up to 60C., 1 hour heating up to 80C., 1 hour heating up to 130C. and 7 hours at 130C. An organi~ solvent soluble product was obtainedO ~he following solvents are useful for solubilization (5% solution) of this polymer at room temperature 0-xylene, benzene, tolu-ene, methylethyl ketone, 1.4 mixture of alcohol~and benzene, chloroform and alcohols.
~; In the following example using pilocarpine free base, the drug is bound ionically to the polymer. ~he attractive ~ features of such a system are (1) slower drug delivery and ¦ (2) capability of delivering pilocarpine as a free base which, ` ;
as such, has a higher potency. Up to now, it was not possi- ; !
ble to delivex pilocarpine as the free base since it is un- ~
.:
stable in this form and as a result is usually delivered as the hydrochloride or nitrate salt.
Ex le XI
1~: : .
Pilocarpine/Poly~-Acetyl-6-0-(Carboxymethyl)-~Glucosamine]
In~erts A 5% solution of poly[~-acetyl-6-0-~carboxgmeth~l)--DLglucosamine~ was prepared in deionized water. ~he solution j was acidified wibh acetic acid and the polymer precipitated by slowly adding this solution to acetone. ~he polymer was dried in vscuo at 40C. overnight. Films were prepared from 5% agueous solutions containing the following relative weights:
Poly~N-Acetyl-6-0-(Carboxy- Drug Dose per Pllocar~ine meth~ D~Glucosamine _ _ 1.5 mg. Strip 9.1 mg 90.9 mg 0.10 mg o 19.4 mg ~0.6 mg 0.24 mg 33-3 mg 66.6 mg 0.50 mg . . . .

. . , - ;. ,, ., , -~

25,160 ~he films were cut into strips approximately 1 ~m x 10 mm weighing 1.5 mg each. In this ma~ner, the drug dosages are delivered from each respective strip, when inserted in the eye.
5Effective medication for a treatment day is obtai~ed b~ placing an insert 1 mm by 10 mm in the human eye.

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Claims (5)

The embodiments of the invention in which an exclusive prop-erty or privilege is claimed are defined as follows:

1. An enzymatically degradable bioerodible drug delivery device for administering a drug to a living mammal characterized in that is consists of a matrix of an enzymatic-ally degradable form of poly(N-acetyl-D-glucosamine), and intimately dispersed therein, an at least slightly water soluble drug.

2. The drug delivery device of Claim 1 in which the matrix is a solvent soluble form of poly(N-acetyl-D-glucosamine) selected from the group consisting of poly[N-acetyl-6-0-(carboxymethyl)-D-glucosamine], poly[N-acetyl-6-0-(2'-hydroxyethyl)-D-glucosamine], and poly[N-acetyl-6-0-(ethyl)-D-glucosamine].

3. The enzymatically degradable bioerodible drug delivery device of Claim 1 in which the enzymatically de-gradable form of poly(N-acetyl-D-glucosamine) is poly(N-acetyl-6-0-(carboxymethyl)-D-glucosamine], and the drug is pilocarpine.

4. The enzymatically degradable bioerodible drug delivery device of Claim 3 which is shaped to conform to the curvature of the eye and is adapted for insertion and reten-tion in the conjunctival sac of the eye.

5. The enzymatically degradable bioerodible drug delivery device of Claim 2 in which the matrix is poly[N-acetyl-6-0-(carboxymethyl)-D-glucosamine], the drug is an anti-fertility agent, and the device is shaped for insertion and retention as an intrauterine contraceptive device.