Controlled-release delivery systems for hormones. A review of their properties and current therapeutic use.

Biomedical engineering approaches used to develop controlled-release delivery systems for hormones are here reviewed regarding system design and therapeutic applications. The biomedical engineering approach uses a system of non-drug components to control the rate and duration of hormone delivery. The non-drug components vary from system to system, but generally include: a reservoir for the hormone; a barrier or regulator to contain the hormone within the reservoir and to control its release; an energy source to remove the hormone from the reservoir; and a pathway for egress of the hormone from the system. Controlled-release delivery systems for hormones discussed in this review include mechanical and osmotic pumps; intraocular, intravaginal and intrauterine platform devices; biodegradable and non-biodegradable subcutaneous implants; and small particulate systems including microcapsules, microspheres and liposomes. Examples of the therapeutic application of the various systems are given along with a discussion of design factors and pharmacological aspects relevant to their clinical use.