An overview of IUD research and implications for the future.

The limitations of nonmedicated intrauterine devices (IUDs) and the potential for improving IUD performance through the addition of pharmacologic agents are discussed. The mechanisms of action of IUDs, particularly of the copper and the progesterone-releasing devices, are reviewed. The development of improved intrauterine contraceptive devices will depend on an understanding of these mechanisms of action. In order to determine the optimal design of intrauterine contraceptives, the effects of the pharmacologic agents will also have to be evaluated, both separately and in combination with the carrier (vector).