IE81128B1 - Biodegradable in-situ forming implants - Google Patents

Description

BIODEGRADABLE IN-SITU FORMING IMPLANTS Technical Field The present invention relates to a composition for producing biodegradable polymers, and more particularly to the use of such polymers for providing syringeable, in-situ forming, solid, biodegradable implants.

Background Art Biodegradable polymers have been used for many years in medical applications. These include sutures, surgical clips, staples, implants, and drug delivery systems. The majority of these biodegradable polymers have been thermoplastic materials based upon glycolide, lactide, e-caprolactone, and copolymers thereof. Typical examples are the polyglycolid'e sutures described in U.S. Patent No. 3,297,033 to Schmitt. the poly(L-lactide-co-glycolide) sutures described in U.S. Patent No. 3,636,956 to Schneider, the poly(L-lactide-co-glycolide) surgical clips and staples described in U.S. Patent No. 4,523,591 to Kaplan et al. . and the drug-delivery systems described in U.S. Patent No. 3,773,919 to Boswell et al.. U.S. Patent No. 3,887,699 to Yolles, U.S. Patent No. 4,155,992 to Schmitt. U.S. Patent No. 4,379,138 to Pitt et al. , and U.S. Patent Nos. 4,130,639 and 4,186,189 to Shalabv et al.

All of the biodegradable polymers described in these patents are thermoplastic materials. Consequently, they can be heated and formed into various shapes such as - 2 fibers, clips, staples, pins, films, etc. Only when heated above their melting point do these polymers become liquid. During their normal use, they are solids.

Although this class of biodegradable polymers has many useful biomedical applications, there are several important limitations to their use in the body where body is defined as that of humans, animals, birds, fish, and reptiles. Because these polymers are solids, all instances involving their use have required initially forming the polymeric structures outside the body, followed by insertion of the solid structure into the body. For example, sutures, clips, and staples are all formed from thermoplastic biodegradable polymers prior to use. When inserted into the body, they retain their original shape rather than flow to fill voids or cavities where they may be most needed. - 3 Similarly, drug-delivery systems using these biodegradable polymers have to be formed outside the body. In such instances, the drug is incorporated into the polymer and the mixture shaped into a certain form such a cylinder, disc, or fiber for implantation. With such solid implants, the drug-delivery system has to be inserted into the body through an incision. These incisions are often larger than desired by the medical profession and lead to a reluctance of the patients to accept such an impl'.nt or drug-delivery system.

The only way to avoid the incision with these polymers is to inject them as small particles, microspheres, or microcapsules. These may or may not contain a drug which can be released into the body.

Although these small particles can be injected into the body with a syringe, they do not always satisfy the demand for a biodegradable implant. Because they are particles, they do not form a continuous film of solid implant with the structural integrity needed for certain prostheses.

When inserted into certain body cavities such as the mouth, a periodontal pocket, the eye, or the vagina where there is considerable fluid flow, these small particles, microspheres, or microcapsules are poorly retained because of their small size and discontinuous nature. In addition, microspheres or microcapsules prepared from these polymers and containing drugs for release into the body are sometimes difficult to produce on a large scale, and their storage and injection characteristics present problems. Furthermore, one other major limitation of the microcapsule or small-particle system is their lack of reversibility without extensive surgical intervention. That is, if there are complications after they have been injected, it is - 4 considerably more difficult to remove them from the body than with solid implants.

Therefore, there exists a need for a composition which provides a biodegradable, polymeric structure useful in overcoming the above-described limitations.

There exists a further need for a composition for providing syringeable, in-situ forming, solid, biodegradable implants which can be used as prosthetic devices and/or controlled delivery systems.

Moreover, there exists a need for such a composition which can provide implants having a range of properties from soft to rigid, so as to be usable with both soft and hard tissue.

Disclosure of the Invention The present invention relates to a composition for forming a solid implant in situ within a body by exposure to body fluids or aqueous fluids, comprising an effective amount of a biocompatible, thermoplastic polymer in a biocompatible organic solvent, the polymer being insoluble in aqueous fluid or body fluid, and the organic solvent being miscible with aqueous fluid or body fluid, characterized in that the polymer is biodegradable.

It further relates to the use of a biocompatible, biodegradable thermoplastic polymer which is insoluble in aqueous fluid or body fluid for the preparation of a composition in a biocompatible organic solvent which is miscible with aqueous fluid or body fluid for forming a biodegradable solid implant in situ within a body by exposure to body fluids or aqueous fluids. - 5 Therefore, the present invention relates to compositions of biodegradable polymers forming in situ prosthetic implants and controlled-release, drug-delivery systems which can be administered as liquids via, for example, a syringe and needle, but which coagulate shortly after dosing to form a solid. The implants are biodegradable because they are made from biodegradable thermoplastic polymers and copolymers.

A thermoplastic system is provided in which a solid, linear-chain, biodegradable polymer or copolymer is dissolved in a solvent, which is nontoxic and water miscible, to form a liquid solution.

By the term miscible, it is understood that the solubility of the organic solvent can range from totally miscible to soluble to dispersible in water, as defined by Hawley's Condensed Chemical Dictionary, 11th Edition, miscibility (1987).

Once the polymer solution is placed into the body where there is sufficient water, the solvent dissipates or diffuses away from the polymer, leaving the polymer to coagulate or solidify into a solid structure. The placement of the solution can be anywhere within the body, including soft tissue such as muscle or fat, hard tissue such as bone, or a cavity such as the periodontal, oral, vaginal, rectal, nasal, or a pocket such as a periodontal pocket or the cul-de-sac of the eye. For drug-delivery systems, the biologically active agent is added to the polymer solution where it is either dissolved to form a homogeneous solution or dispersed to form a suspension or dispersion of drug within the polymeric solution. When the polymer solution is exposed to body fluids or water, the solvent diffuses away from the polymer-drug mixture and water diffuses into the mixture where it coagulates the polymer thereby trapping or encapsulating the drug within the polymeric matrix as the implant solidifies. The release of the drug then follows the general rules for diffusion or dissolution of a drug from within a polymeric matrix. - 6 With the inventive thermoplastic polymer systems, the advantages of liquid application are achieved. For example, the polymer composition may be injected via syringe and needle into a body while it is in liquid form and then left in-situ to form a solid biodegradable implant structure. The need to form an incision is eliminated, and the implant will assume the shape of its cavity. Furthermore, a drug-delivery vehicle may be provided by adding a biologically active agent to the liquid prior to injection. Once the implant is formed, it will release the agent to the body and then biodegrade. The term biologically active agent means a drug or some other substance capable of producing an effect on a body.

It is an object of the present invention, therefore, to provide a composition for producing in-situ biodegradable solid implants.

It is also an object of the present invention to provide such a composition which may be useful in producing syringeable, in-situ forming, solid biodegradable implants.

It is a further object of the present invention to provide such an implant which can be used in a controlled-release delivery system for biological agents.

It is a further object of the present invention to provide implants having a range of properties from soft and elastomeric to hard and rigid, so as to be usable with both soft and hard tissue. - 7 Best Mode of Carrying Out the Invention The present invention relates to compositions of biodegradable polymers forming implants in-situ. The present invention also relates to a liquid biodegradable polymeric delivery system that can be injected into a body where it forms a solid and releases a biologically active agent at a controlled rate. The biodegradable polymeric systems are thermoplastic polymers dissolved in a biocompatible solvent.

A themoplastic system is provided in which a solid, linear-chain, biodegradable polymer is dissolved in a biocompatible solvent to form a liquid, which can then be administered via a syringe and needle. Examples of biodegradable polymers which can be used in this application are polylactides, polyglycol ides, polycaprolactones, polyanhydrides, polyamides, polyurethanes, polyesteramides, polyorthoesters, polydioxanones, polyacetals, polyketals, polycarbonates, polyorthocarbonates, polyphosphazenes, polyhydroxybutyrates, polyhydroxyvalerates, polyalkylene oxalates, polyalkylene succinates, poly (amino acids), and copolymers, terpolymers, or combinations or mixtures of the above materials.

The preferred polymers are those which have a lower degree of crystallization and are more hydrophobic. These polymers and copolymers are more soluble in the biocompatible solvents than the highly crystalline polymers such as polyglycolide which also have a high degree of hydrogen-bonding. Preferred materials with the desired solubility parameters are the polylactides, polycaprolactones, and copolymers of these with glycolide in which there are more amorphous regions to enhance solubility. - 8 It is also preferred that the solvent for the biodegradable polymer be non-toxic, water miscible, and otherwise biocompatible. Solvents that are toxic should not be used to inject any material into a living body. The solvents must also be biocompatible so that they do not cause severe tissue irritation or necrosis at the site of implantation. Furthermore, the solvent should be water miscible so that it will diffuse quickly into the body fluids and allow water to permeate into the polymer solution and cause it to coagulate or solidify. Examples of such solvents include N-methyl-2-pyrrolidone, 2pyrrolidone, ethanol, propylene glycol, acetone, methyl acetate, ethyl acetate, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, caprolactam, decylmethylsulfoxide, oleic acid, and 1dodecylazacycloheptan-2-one and combinations and mixtures thereof.

The preferred solvents are N-methy1-2-pyrrolidone, 2-pyrrolidone, dimethyl sulfoxide, and acetone because of their solvating ability and their compatibility.

The solubility of the biodegradable polymers in the various solvents will differ depending upon their crystallinity, their hydrophilicity, hydrogen-bonding, and molecular weight. Thus, not all of the biodegradable polymers will be soluble in the same solvent, but each polymer or copolymer should have its optimum solvent.

Lower molecular-weight polymers will normally dissolve more readily in the solvents than high-molecular-weight polymers. As a result, the concentration of a polymer dissolved in the various solvents will differ depending upon type of polymer and its molecular weight. Conversely, the higher molecular-weight polymers will normally tend to coagulate or solidify faster than the very low-molecularweight polymers. Moreover the higher molecular-weight - 9 polymers will tend to give higher solution viscosities than the low-molecular-weight materials. Thus for optimum injection efficiency, the molecular weight and the concentration of the polymer in the solvent have to be controlled.

For example, low-molecular-weight polylactic acid formed by the condensation of lactic acid will dissolve in N-methyl-2-pyrrolidone(NMP) to give a 73% by weight solution which still flows easily through a 23-gauge syringe needle, whereas a higher molecular-weight poly(DLlactide) (DL-PLA) formed by the additional polymerization of DL-lactide gives the same solution viscosity when dissolved in NMP at only 50% by weight. The higher molecular-weight polymer solution coagulates immediately when placed into water. The' low-molecular-weight polymer solution, although more concentrated, tends to coagulate very slowly when placed into water.

For polymers that tend to coagulate slowly, a solvent mixture can be used to increase the coagulation rate. Thus one liquid component of the mixture is a good solvent for the polymer, and the other component is a poorer solvent or a non-solvent. The two liquids are mixed at a ratio such that the polymer is still soluble but precipitates with the slightest increase in the amount of non-solvent, such as water in a physiological environment.

By necessity, the solvent system must be miscible with both the polymer and water. An example of such a binary solvent system is the use of NMP and ethanol for low-molecularweight DL-PLA. The addition of ethanol to the NMP/polymer solution increases its coagulation rate significantly.

It has also been found that solutions containing very high concentrations of high-molecular-weight polymers sometimes coagulate or solidify slower than more dilute solutions. It is suspected that the high concentration of - 10 polymer impedes the diffusion of solvent from within the polymer matrix and consequently prevents the permeation of water into the matrix where it can precipitate the polymer chains. Thus, there is an optimum concentration at which the solvent can diffuse out of the polymer solution and water penetrates within to coagulate the polymer.

In one envisioned use of the thermoplastic system, the polymer solution is placed in a syringe and injected through a needle into the body. Once in place, the solvent dissipates, the remaining polymer solidifies, and a solid structure is formed. The implant will adhere to its surrounding tissue or bone by mechanical forces and can assume the shape of its surrounding cavity. Thus, the biodegradable polymer solution can be injected subdermally like collagen to build up tissue or to fill in defects. It can also be injected into wounds including burn wounds to prevent the formation of deep scars. Unlike collagen, the degradation time of the implant can be varied from a few weeks to years depending upon the polymer selected and its molecular weight. The injectable polymer solution can also be used to mend bone defects or to provide a continuous matrix when other solid biodegradable implants such as hydroxyapatite plugs are inserted into bone gaps. The injectable system can also be used to adhere tissue to tissue or other implants to tissue by virtue of its mechanical bonding or encapsulation of tissue and prosthetic devices.

Another envisioned use of the thermoplastic system is to provide a drug-delivery system. In this use, a bioactive agent is added to the polymer solution prior to injection, and then the polymer/solvent/agent mixture is injected into the body. In some cases, the drug will also be soluble in the solvent, and a homogenous solution of polymer and drug will be available for injection. In other cases, the drug will not be soluble in the solvent, and a - 11 suspension or dispersion of the drug in the polymer solution will result. This suspension or dispersion can also be injected into the body. In either case, the solvent will dissipate and the polymer will solidify and entrap or encase the drug within the solid matrix. The release of drug from these solid implants will follow the same general rules for release of a drug from a monolithic polymeric device. The release of drug can be affected by the size and shape of the implant, the loading of drug within the implant, the permeability factors involving the drug and the particular polymer, and the degradation of the polymer. Depending upon the bioactive agent selected for delivery, the above parameters can be adjusted by one skilled in the art of drug delivery to give the desired rate and duration of release.

The term drug or bioactive (biologically active) agent as used herein includes without limitation physiologically or pharmacologically active substances that act locally or systemically in the body. Representative drugs and biologically active agents to be used with the syringeable, in-situ forming solid implant systems include, without limitation, peptide drugs, protein drugs, desensitizing agents, antigens, vaccines, anti-infectives, antibiotics, antimicrobials, antiallergenics, steroidal anti-inflammatory agents, decongestants, miotics, anticholinergecs, sympathomimetics, sedatives, hypnotics, psychia energizers, tranquilizers, androgenic steroids, estrogens, progestational agents, humoral agents, prostaglandins, analgesics, antispasmodics, antimalarials, antihistamines, cardioactive agents, non-steroidal antiinflammatory agents, antiparkinsonian agents, antihypertensive agents, β-adrenergic blocking agents, nutritional agents, and the benzophenanthridine alkaloids. To those skilled in the art, other drugs or biologically active agents that can be released in an aqueous environment can be utilized in the described injectable - 12 delivery system. Also, various forms of the drugs or biologically active agents may be used. These include without limitation forms such as uncharged molecules, molecular complexes, salts, ethers, esters, amides, etc., which are biologically activated when injected into the body.

The amount of drug or biologically active agent incorporated into the injectable, in-situ, solid forming implant depends upon the desired release profile, the concentration of drug required for a biological effect, and the length of time that the drug has to be released for treatment. There is no critical upper limit on the amount of drug incorporated into the polymer solution except for that of an acceptable solution or dispersion viscosity for injection through a syringe heedle. The lower limit of drug incorporated into the delivery system is dependent simply upon the activity of the drug and the length of time needed for treatment.

In all cases, the solid implant formed within the injectable polymer solution will slowly biodegrade within the body and allow natural tissue to grow and replace the impact as it disappears. Thus, when the material is injected into a soft-tissue defect, it will fill that defect and provide a scaffold for natural collagen tissue to grow. This collagen tissue will gradually replace the biodegradable polymer. With hard tissue such as bone, the biodegradable polymer will support the growth of new bone cells which will also gradually replace the degrading polymer. For drug-delivery systems, the solid implant formed from the injectable system will release the drug contained within its matrix at a controlled rate until the drug is depleted. With certain drugs, the polymer will degrade after the drug has been completely released. With other drugs such as peptides or proteins, the drug will be completely released only after the polymer has degraded to - 13 a point where the non-diffusing drug has been exposed to the body fluids.

DETAILED DESCRIPTION OF EXAMPLES The following examples are set forth as representative of the present invention. These examples are not to be construed as limiting the scope of the invention as these and other equivalent embodiments will be apparent in view of the present disclosure, figures, and accompanying claims.

EXAMPLE 1 Poly(DL-lactic acid) was prepared by the simple polycondensation of lactic acid. No catalysts were used, and the reaction times were varied to produce polymers with I - 14 different theoretical molecular weights. These polymers were designated as DL-PLA oligomers. A quantity of the solid oligomer was dissolved in NMP to give a 68:32 ratio of polymer to solvent. Sanguinarine chloride(Sacl), a benzophenanthridine alkaloid with antimicrobial activity especially toward periodontal pathogens, was added to the polymer solution to give a 2% by weight dispersion of the drug in the total mixture. The dispersion of drug and polymer solution was then injected into a dialysis tube (diameter of 11.5mm) with a sterile disposable syringe without a needle. Each end of the 6-in. length of dialysis tubing was tied with a knot to prevent loss of the drug/polymer mass, and the tube with the injected material was placed in a pH 7 Sorenson’s buffer receiving fluid maintained at 37’ c. Upon immersion in the receiving fluid, the drug/polymer mass/coagulated into a solid mass, and the drug began to be released from the polymer as indicated by an orange-red color in the receiving fluid.

The quantity of solution injected into the dialysis tube was about 250 μΐ» or about 100 mg of solids.

The dialysis tubing was selected to have a molecular-weight cutoff of about 3,500. With this molecular-weight cutoff, the SaCl released from the polymer could easily diffuse through the walls of the tubing, but any solid polymer would be retained. The dialysis tubing containing the drug/polymer matrix was removed frequently and placed in a bottle of fresh receiving fluid. The old receiving fluid containing the released drug was then acidified to a pH of 2.76 to convert all released drug to the iminium ion form of the drug, and the concentration of drug was determined by measuring the ultraviolet absorption (UV) at a wavelength of 237 nm. The cumulative mass of drug released and the cumulative fraction were then calculated and plotted as a function of time.

Approximately 60% of the drug was released in the first - 15 day, 72% after 2 days, 85% after 5 days, 90% after 9 days, and 97% after 14 days.

EXAMPLE 2 Ethoxydihydrosanguinarine(SaEt), the ethanol ester of sanguinarine, was added to the same DL-PLA oligomer/NMP solution described in Example 1. SaEt dissolved in the polymer solution to give a homogenous solution of drug and polymer. Approximately 250 gL of the solution was added to receiving fluid And the release of drug measured as described in Example 1. The release of SaEt was slower than that for SaCl as expected because of its lower water solubility. After the first day, approximately 45% was released, 52% after 2 days, 60% after 5 days, 70% after 9 days, and 80% after 14 days.

EXAMPLE 3 Poly (DL-lactide) with an inherent viscosity of 0.08 dL/g and a theoretical molecular weight of 2,000 was prepared by the ring-opening polymerization of DL-lactide using lauryl alcohol as the initiator and stannous chloride as the catalyst. This polymer was then dissolved in NMP to give a 40% by weight polymer solution. SaCl was dispersed in the solution of this polymer in NMP to give a 1.5% by weight dispersion of the drug in the solution and the release rate determined as described in Example 1. The release rate of the drug from this higher molecular-weight polymer was slower than from the DL-PLA oligomer. After the first day, approximately 32% was released, 40% after 2 days, 45% after 5 days, and 50% after 15 days.

EXAMPLE 4 SaEt was added to the same polymer solution of DL-PLA in NMP as described in Example 3. A homogenous solution with the drug at 1.5% by weight was obtained. The release of drug from this solution determined using the same procedure described in Example 1 gave a much slower - 16 release of SaEt than from the DL-PLA oligomer. After the first day approximately 8% was released, 14% after 2 days, 20% after 5 days, 23% after 9 days, and 28% after 14 days.

EXAMPLE 5 The effect of drug loading on the release of drug from the polymer solutions were demonstrated by adding Sacl to a 40% by weight of DL-PLA oligomer in NMP. The drug was dispersed in the polymer solution to give 2, 7 and 14% by weight dispersions. The release of driig from these formulations using the same procedure as described in Example 1 showed that the higher drug loadings gave a lower fractional rate of release as normally obtained for matrix delivery systems with diffusional release. The 2%-loaded formulation gave 65% release after 1 day, 75% after 2 days, and 88% after 5 days; the 7%’iloaded formulation gave 48% release after 1 day, 52% after 2 days, and 58% after 5 days; and the 14%-loaded formulation gave 38% release after 1 day, 43% after 2 days, and 49% after 5 days.

EXAMPLE 6 .

Poly (DL-lactide-co-glycolide) was prepared by the ring-opening polymerization of a mixture of DL-lactide and glycolide using lauryl alcohol as the initiator and stannous chloride as the catalyst. The proportions of the two monomers were adjusted so that the final copolymer(DLPLG) had a 50:50 ratio of the two monomers as determined by nuclear magnetic resonance spectrophotometry. The initiator was also adjusted to give a copolymer with a theoretical molecular weight of 1500 daltons. The copolymer was dissolved in NMP to give a 70% by weight polymer solution. SaCl was added to this solution to give a 2% by weight dispersion of the drug in the polymer solution. The release of drug from this formulation was determined using the same procedure described in Example l.

A much lower release rate was obtained from the copolymer than from the DL-PLA oligomer or DL-PLA 2000 molecular - 17 weight materials. After 2 days approximately 7% of the drug was released, 10% after 5 days, 12% after 7 days, and 16% after 14 days.

EXAMPLE 7 SaEt was added to the same solution of DL-PLG in NMP as described in Example 6 to give a 2% by weight solution of the drug. The release of drug from this formulation was determined by the same procedure as described previously. The release rate of SaEt from this formulation was identical to that for SaCl described in Example 6.

EXAMPLE 8 Tetracycline as the free base (TCB) was added to the same solution of DL-PLG /in NMP as described in Example 6. The drug dissolved completely in the polymer solution to give a 2.4% by weight solution of the drug.

The release of the drug from this formulation was determined by a similar procedure to that described in Example 1 except the receiving fluid was not acidified to a pH of 2.76 and the concentration of TCB was determined by UV absorption at the wavelength appropriate for the drug. The release of TCB from this formulation was more linear and at a much higher rate than that for SaCl or SaEt from the same copolymer. After 1 day approximately 44% of the drug was released, 54% after 2 days, 68% after 5 days, 73% after 6 days, 80% after 7 days, 87% after 9 days, 96% after 12 days, and 100% after 14 days.

EXAMPLE 9 Tetracycline as the hydrochloride salt (TCH) was added to the same solution of DL-PLG in NMP as described in Example 6. The salt form of the drug also dissolved completely in the polymer solution. The release of drug from this formulation was determined as described in Example 8 and found to be similar to that for the free base - 18 except for a slightly lower rate. After 1 day approximately 32% of the drug was released, 40% after 2 days, 57% after 5 days, 64% after 6 days, 75% after 7 days, 82% after 9 days, 92% after 12 days, and 100% after 14 days.

EXAMPLE 10 DL-PLA with an inherent viscosity of 0.26 dL/g and a theoretical molecular weight of approximately 10,000 daltons was prepared by the ring-opening polymerization of DL-lactide using lauryl alcohol as the initiator and stannous chloride as the catalyst. The polymer was dissolved in NMP to give a 50% by weight polymer solution.

A quantity of the polymer solution (100 mL) was injected subdermally into rabbits, and the tissue reaction was compared to that of a USP negative plastic. The test sites were evaluated for signs of local irritation, in accordance with the Draize method, immediately after injection, at 1 and 6 hours post injection, and once daily thereafter until scheduled sacrifice at 7, 14 or 21 days. The reaction at the test sites was equivalent to that at the control USP negative plastic. The polymer solution (100 jiL) was also administered subgingivally into sites created by dental extractions in Beagle dogs. Control sites were flushed with saline solution. The dogs were examined daily for signs of mortality, pharmacotoxic effects, body weights, and local gingival irritation. The animals were sacrificed at 15 and 21 days. No distinct differences were noted between the control and test sites.

EXAMPLE 11 DL-PLA with an inherent viscosity of 0.126 dL/g and a molecular weight of about 10,000 was dissolved in NMP to give a 50% by weight polymer solution. SaCl was added to the polymer solution to give a 2.4% by weight dispersion. This material was loaded into a l-cc disposable syringe fitted with a 23-gauge blunted-end - 19 syringe needle, and the material was inserted into the periodontal pocket of a greyhound dog. The material flowed easily out of the narrow syringe tip. The polymer precipitated or coagulated into a film or solid mass when it contacted the saliva and fluid within the pocket. The dog was observed over a time of 2 weeks during which the mass of material remained within the pocket, adhering to tissue surrounding the pocket, and slowly changing color from a light orange to a pale white. The crevicular fluid from the pocket containing the implant*was sampled during this 2-week period using Periostrips which are small strips of paper that are placed at the entrance to the periodontal pocket to wick up small quantities of the crevicular fluid within the pocket. The volume of fluid collected is determined using a Periotron which measures the changes in conductance of the paper strip. The Periotron is calibrated before use with a known volume of serum. The paper strip containing the collected fluid is then extracted with a solution of 0.5% by volume of hydrochloric acid in methanol and injected into a liguid chromatograph where the quantity of drug is determined by reference to a known concentration of the same compound. The quantity of SaCl extracted from the paper strip is divided by the quantity of crevicular fluid collected to calculate the concentration of drug in the fluid. With this technique, the concentration of SaCl within the crevicular fluid from the periodontal pocket with the polymeric delivery system was determined to be almost constant during the 2 weeks of observation. The Sacl concentration in the crevicular fluid was 63.2 pg/mL after 3 days, 80.2 pg/mL after 7 days, 67.8 pg/mL after 10 days, and 70.5 gg/mL after 14 days.

Claims (28)

Claims:

1. A composition for forming a solid implant in situ within a body by exposure to body fluids or aqueous fluids, comprising an effective amount of a biocompatible, thermoplastic polymer in a biocompatible organic solvent, the polymer being insoluble in - aqueous fluid or body fluid, and the organic solvent being miscible with aqueous fluid or body fluid, characterized in that the polymer is biodegradable.

2. The composition of claim 1, in which the IQ thermoplastic polymer is selected from polylactides, polyglycolides, polycaprolactones, polydioxanones, polycarbonates, polyhydroxybutyrates, polyalkylene oxalates, polyanhydrides, polyamides, polyesteramides, polyurethanes, polyacetals, 15 polyketals, polyorthocarbonates, polyphosphazenes, polyhydroxyvalerates, polyalkylene succinates, polyorthoesters, poly(amino acids), and copolymers terpolymers and combinations and mixtures thereof.

3. The composition of claim 1 or 2, in which the polymer is selected from polylactides, polycaprolactones and copolymers thereof with glycolide, and copolymers of 25 lactide with caprolactone.

4. The composition of any one of claims 1 to 3, in which the solvent is selected from N-methyl-2-pyrrolidone, 2-pyrrolidone, acetone, methyl acetate, ethyl ace30 tate, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, caprolactam, - 21 decylmethyl sulfoxide, oleic acid, ethanol, propylene glycol and l-dodecylazacycloheptan-2-one and combinations and mixtures thereof.

5. The composition of any one of claims 1 to 4, further comprising an effective amount of a biologically active agent.

6. The composition of any one of claims 1 to 5, in which the solvent is a solvent mixture comprising a first solvent which dissolves the polymer and a second solvent which is a poor solvent for the polymer, the first and second solvents being present in the mixture at a ratio such that the polymer is soluble therein, so that the polymer is precipitated or coagulated from that solution upon placing the solution within the body.

7. The composition of claim 5 or 6, Including a biologically active agent which is a therapeutic agent.

8. The composition of claim 7, in which the biologically active agent comprises a benzophenanthridine alkaloid.

9. The composition of claim 8, in which the alkaloid comprises sanguinarine chloride or ethoxydihydrosanguinarine.

10. The composition of claim 7, in which the biologically active agent comprises a tetracycline base. The composition of claim 7, in which the biologically active agent comprises tetracycline hydrochloride.

11. - 22

12. The composition of any one of claims 6 to 11, in which the polymer is a lactide polymer and the second solvent is selected from ethanol or propylene glycol. 5

13. The composition of any of claims 1-3, in which the polymer is a copolymer of a biodegradable, water-insoluble monomer and a biodegradable water-soluble monomer, and the amount of water-insoluble monomer is sufficient to render the copolymer water-insoluble.

14. The composition of claim 13, in which the water-soluble monomer is selected from malic acid, vinyl pyrrolidone, and ethylene glycol.

15. 15. A composition of any one of claims 1-14 for forming an implant in the periodontal pocket or in dental extraction sites.

16. A composition of any one of claims 1-14 for forming an implant in a bone defect or in a wound.

17. A composition of any one of claims 1-14 for forming an implant for adhering tissue to tissue or another implant to tissue.

18. A composition of any one of claims 1-14 for forming an implant for building up tissue or filling in a defect. 30 ·

19. The use of a biocompatible, biodegradable thermoplastic polymer which is insoluble in aqueous fluid or body fluid for the preparation of a composition in a biocompatible organic solvent which is miscible with aqueous fluid or body fluid for forming -23 a biodegradable solid implant in situ within a body by exposure to a body fluid or an aqueous fluid.

20. The use of claim 19, in which the polymer is selected 5 from polylactides, polyglycolides, polycaprolactones, polydioxanones, polycarbonates, polyhydroxybutyrates, polyalkylene oxalates, polyanhydrides, polyamides, polyesteramides, polyurethanes, polyacetals, polyketals, polyorthocarbonates, polyphosphazenes, 10 polyhydroxyvalerates, polyalkylene succinates, poly(amino acids), and polyorthoesters, and copolymers, terpolymers and combinations and mixtures thereof.

21. The use of claim 20, in which the polymer is selected from polylactides, polycaprolacrones and copolymers thereof with glycolide, and copolymers of lactide with caprolactone. C

22. IhQ usjar of any of claims 19 to 21, in which the solvent is selected from N-methyl-2-pyrrolidone, 2-pyrrolidone, acetone, methyl acotate, ethyl acetate, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, tetrahydrofuran and caprolactam, decylmethyl sulfoxide, oleic acid, ethanol, propylene glycol and l-dodecylazacycloheptan-2-one and combinations and mixtures thereof.

23. The use of any one of claims'l9 to 22, wherein the solvent is a solvent mixture comprising a first solvent which dissolves the polymer and a second solvent which is a poor solvent for the polymer, the first and second solvents being present in the mixture 35 at a ratio such that the polymer is soluble therein. -

24. 24. The use of claim 53, wherein the polymer is a lactide polymer, and the second solvent is selected from ethanol and propylene glycol.

25. The use of any of claims 19 to 22, in which the polymer is a copolymer of a biodegradable, water-insoluble monomer and a biodegradable water-soluble monomer, and the amount of waterinsoluble monomer is sufficient to render the copolymer waterinsoluble.

26. ihe use of claim 25, in which the water-soluble monomer is selected from malic acid, vinyl pyrrolidone, and ethylene glycol.

27. A composition according to any of claims 1-18 for forming a solid implant in-situ within a body substantially as hereinbefore described by way of example.

28. The use according to any of claims 19-26 of a biocompatible, biodegradable thermoplastic polymer as hereinbefore described by way of example.