Male contraception.

Currently approved male-directed contraceptive methods include condoms and vas occlusion. Vas occlusion is very effective but is intended to be non-reversible. Condoms have a relatively high failure rate, at least partially due to compliance problems and are not accepted by many couples. The only other male-oriented methods in clinical trials utilize the administration of testosterone alone or its combination with another gonadotropin-suppressing agent such as a progestin or a gonadotropin-releasing hormone antagonist. Studies published in the 1990s demonstrated that a testosterone-containing hormonal contraceptive method suppressed spermatogenesis to azoospermia in most men and severe oligozoospermia in the remaining. The contraceptive efficacy after treatment with testosterone alone was comparable to that of female hormonal methods. Having proven that reversible male contraception is a reality, present trials are attempting to identify the best androgen delivery system and the most effective androgen plus progestin preparation. It is likely that the first marketed male hormonal contraceptive method will be a long-acting (injectable or implant) combination of an androgen plus a progestin. Research is continuing to identify other target areas for male contraceptive development, including agents with post-testicular and epididymal sites of action.