PIP: A controlled release system utilizes a polymer matrix or pump as a rate-controlling device to deliver the drug in a fixed, predetermined pattern for a desired time period. These systems have the following advantages compared to other methods of administration: 1) plasma drug levels are continuously maintained in a therapeutically desirable range, 2) harmful side effects from systemic administration can be reduced or eliminated by local administration from a controlled release system, 3) drug administration may be improved and facilitated in underpriviledged areas where good medical supervision is not available, 4) administration of drugs that have short in vivo half lives may be greatly facilitated, 5) continuous small amounts of drug may be less painful than several large doses, 6) patient compliance may be improved, and 7) this method is relatively less expensive and less wasteful of the drug. Disadvantages include possible toxicity, need for surgery to implant the system, possible pain, and difficulty in shutting off release if necessary. Two types of diffusion-controlled systems have been developed. The reservoir is a core of drug surrounded with a polymer film. The 2nd type, the matrix, is one in which the drug is uniformly distributed through a polymer. In chemically controlled systems, the rate of drug release is regulated by a chemical reaction with the polymer. In solvent activated systems a swelling or osmotic mechanism is involved. Pharmaceutical applications have been made in ocular disease with the Ocusert, a reservoir system for glaucoma therapy and which is not widely used, and in contraception with 4 systems. These systems are: 1) subdermal implants of nonbiodegradable polymers such as Norplant, 6 capsules of 36 mg levonorgestrel; 2) subdermal implant of biodegradable polymers; 3) steroid releasing IUD; and 4) vaginal rings, which are silicone-coated. Other applications have been made in the areas of dentistry, immunization, anticoagulation, cancer, narcotic antogonists, and insulin delivery. Transdermal delivery involves placing a polymeric system containing a contact adhesive on the skin.