Gossypol: a male contraceptive with potential?
The serendipitous discovery of gossypol by the Chinese in 1978 may represent the most significant advance ever made in terms of male contraception. Protection from pregnancy has been achieved in 99% of couples who use gossypol. The contraceptive effect seems to be maintainable through a dose of 50 mg/week. Azoospermia can persist for as long as 4 years after gossypol discontinuation. The incidence of overt toxicity in men taking contraceptive doses of gossypol is low although fatigue changes in libido loss of appetite and headache have been reported. Hypokalemia the most potentially life-threatening side effect occurs in an estimated 10% of men who use gossypol for contraception. There is a need for more evaluation of the cardiovascular action of contraceptive doses of gossypol. Animal studies have revealed marked species differences in sensitivity to gossypols contraceptive action. There is no evidence to date that gossypol has adverse effects on the outcome of subsequent pregnancies or on fetal development although any drug that interferes with the production and maturation of spermatozoa should be closely monitored from the perspective of reproductive toxicity. It is unlikely that the contraceptive activity of gossypol can be explained by a single molecular event. Development of the contraceptive potential of gossypol is dependent on chemical modifications and the discovery of a derivative with a safe therapeutic ratio. Overall although gossypol has proven to be an efficient inexpensive means of fertility control the side effects of hypokalemia and possibly permanent infertility make it unacceptable at this time.