It is often desirable to administer drugs using controlled- or sustained-release formulations that can maintain therapeutic blood levels of the drug over extended periods of time. These controlled release formulations reduce the frequency of dosing, for enhanced convenience and compliance, and also reduce the severity and frequency of side effects. By maintaining substantially constant blood levels and avoiding blood level fluctuations of the drug, such as are associated with conventional immediate release formulations that are administered several times a day, controlled- or sustained-release formulations can provide a better therapeutic profile than is obtainable with conventional immediate release formulations.
Known methods for controlled- or sustained-drug release include implanted devices, such as osmotic pumps, and drug dispersed in a biocompatible polymer matrix, which can be implanted, administered orally, or injected. Examples of biocompatible polymers used in such applications include poly(lactic acid) and poly(lactic acid-co-glycolic acid). The polymer typically undergoes slow hydrolysis in vivo to continually release the entrapped drug over time. The polymer degradation products are non-toxic and absorbed or metabolized by the body. For example, when the biocompatible polymer is poly(lactic acid) or poly(lactic acid-co-glycolic acid), the degradation products are the parent acids, lactic acid and glycolic acid, which are absorbed by the body.
U.S. Pat. Nos. 6,887,487 and 6,946,137 disclose compositions of a salt of a pharmacologically active compound and a lipophilic counterion and a pharmaceutically acceptable water soluble solvent that are combined together to provide an injectable composition. When injected into an animal at least a part of the composition precipitates to form a depot that slowly releases the pharmacologically active compound over time.
U.S. patent application no. US 2004/0220264 discloses compositions, methods of making the compositions, and uses of compositions that include a molecular complex between an acidic pharmaceutical drug and a functional substance. The functional substance can be an alkaline amino acid, an amino acid amide, an amino acid ester, or a related amino acid. The compositions are allegedly useful for delivering the drug into cutaneous tissue.
U.S. patent application no. US 2004/0197408 discloses formulations of a diblock copolymer having a hydrophobic block and hydrophilic block, an additive selected from an amino acid, and an oligopeptide. The formulations, when admixed with water, form drug delivery vehicles in micellar form.
There remains a need in the art, however, for drug containing pharmaceutical compositions, suitable for injection or implantation, wherein the formulation provides controlled- or sustained-release of the drug.
Citation of any reference in Section 5 of this application is not to be construed that such reference is prior art to the present application.