A New Long-Acting Injectable Microcapsule System for the Administration of Progesterone

• Published in: Fertility and sterility Vol. 31; no. 5; pp. 545 - 551
• Main Authors: Beck, Lee R., Cowsar, Donald R., Lewis, Danny H., Cosgrove, Robert J., Riddle, Charles T., Lowry, Suzanne L., Epperly, Thomas
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.1979
• Subjects: Animals; Contraceptive Agents - administration & dosage; Delayed-Action Preparations; Drug Evaluation, Preclinical; Female; Injections, Intramuscular; Lactates; Microspheres; Papio; Polymers; Population; Progesterone - administration & dosage; Rats; Progestational Hormones; Contraceptive Agents, Progestin; In Vitro; Biology; Contraception; Hormones; Family Planning; Research Methodology; Endocrine System; Biodegradable Delivery Systems; Progesterone > administraction and dosage; Clinical Research; Contraceptive Methods; Injectables; Physiology; Animals, Laboratory
• ISSN: 0015-0282; 1556-5653
• DOI: 10.1016/S0015-0282(16)44002-1

A long-acting injectable microcapsule system for the controlled-release systemic administration of progesterone (P4) is described. The system consists of microcapsules made of the biodegradable polymer, d,l-polylactic acid, which contain crystalline P4. Following injection, P4 is released from the microcapsules by diffusion and biodegradation of the polymer matrix. The rate of P4 release from the prototype microcapsule system in vivo is 1.3 µg of P4/day/mg of microcapsules, and the duration of release is 30 days. Vaginal estrous cycles in rats and cyclic ovarian function in baboons were inhibited for 1 month following a single injection of P4 microcapsules. The effects of continuous progesterone therapy on reproductive function in both rats and baboons are dose-dependent. The utility of the system as a once-a-month injectable contraceptive is established in the baboon model.