Experimental methods of contraception

While most new contraceptives currently in development incorporate existing contraceptive agents into new delivery systems, several types of contraceptives with novel mechanisms of action are making steady progress. The antiprogestin mifepristone (better known as RU 486) is being tested as an ovulation inhibitor, as a once-a-month pill, and as a postcoital contraceptive. An antiestrogen, Centchroman (Hindustan Latex, India), is in use in India as a once-a-week, nonsteroidal pill. The development of more potent pituitary gonadotropin antagonists has improved their potential to block ovulation in women and to inhibit spermatogenesis in men (which requires concurrent administration of testosterone). Another promising male contraceptive is an intraluminal vas occlusion plug tested extensively in China that can be removed with no apparent detriment to future fertility. Finally, several types of immunocontraceptives could become the most specific form of fertility control by directing an antibody response against the fertilized or unfertilized egg or against sperm.