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Abstract
Steroidal nonsteroidal plant-derived gonadotropin-related and immunological agents investigated for control of male fertility are reviewed with brief descriptions of their effects and illustrations of their structures. The physiology of the male reproductive system is presented as an introduction: an ideal male antifertility agent would inhibit spermatogenesis at the level of the Sertoli cells without affecting endogenous androgen production by Leydig cells needed for libido and potency. Androgens down-regulate their own production at physiological levels but few long-acting orally active derivatives are available. Anti-androgens with mixed androgen and progestin activity combined with a pure androgen are potentially useful. Androgen-progestin combinations are being tested by WHO as implants. Dozens of miscellaneous nonsteroidal compounds have been discovered serendipitously to have antifertility activity in men or male animals including alkylating agents antimetabolites antibiotics sulfa derivatives fungicides trichomonocides amebicides alpha blockers antimalarials coumarins and carbohydrate derivatives. Various plant alkaloids have been screened. Those of Hibiscus Vitex and Plumbago species as well as Tripterygium wilfordii glycosides which are being evaluated in combination with gossypol are mentioned here. Gossypol has been thoroughly tested in China but rejected because of its side effects particularly hypokalemic paralysis its low therapeutic index and uncertain recovery of fertility. Gonadotropin-releasing hormone (GnRH) agonists and antagonists are being researched in combination with androgens with some success. The GnRH antagonists to date have low activity or cause histamine-related side effects at higher doses; the androgens require a new route such as a long-acting implant to overcome the need for daily injections. Immunological contraception for males has not progressed beyond the research stage.
Published Version
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