Polymers having slow release function and their applications

The research of giving slow releasing property to drugs by compounding them with suitable matrices and forming has been carried out actively in order to minimize the adverse effect, to reduce the frequency of administration and to improve the bioavailability of such drugs. The slow release function of drugs may be acquired by the copolymerization with synthetic and natural polymers. Drugs are mixed with monomers, and the mixture is polymerized by means of heat, light or radiation (gamma ray or electron beam). Various physical and chemical factors influencing on the rate of release are shown. The compound capsules of drugs and polymers may be used for chemotherapy, enzyme and hormone therapy, immunotherapy, artificial organs, medical and pharmaceutical applications in the form of suppositary, and administration by mucous membrane, subcutaneous and intra-fascia contact or burying. Mytomycin (MMC) of 1.6 mg/kg (LD50 of i.v. injection) or 3.2 mg/kg (LD50 x 2) was implanted in the abdomen of dogs. The release of MMC from the implanted capsules was relatively localized to the vicinity of implantation. More hydrophilic polymer (39 % water retention, for example, hydroxyethylmetacrylate polymer) gave more death (toxicity) cases than less hydrophilic one (2 % water retention, for example, diethylglycoldimetacrylate polymer) in the mice with Ehrlich ascites cancer cells, 5 x 106 cells/0.2 ml. Because of the nature of locally limited release of the drug, the capsules of anti-cancer drugs, analgesics, antibiotics, hormone, etc. should be delivered to disease foci by means of a fiber scope technique, or intravascular microcapsules. (Yamashita, S.)