A chemical known as lonidamine prevents developing sperm from staying attached to the cells lining the seminiferous tubule and causes infertility in rats and men, says the Population Council's C. Yan Cheng. He and his colleagues have developed two less toxic compounds that share the core structure of lonidamine, Cheng reported in June at the Endocrine Society meeting in Toronto. Rats given the drugs orally become infertile, with no signs of side effects, and their fertility returns once the drugs are discontinued, he says. Other possibilities for fast-acting and easily reversed contraceptives come from compounds known to interfere with chemicals that initiate the movement of sperm tails or that allow sperm to penetrate the coverings of the egg. Another possible approach is called immunocontraception.
Scientists propose that either women or men can be immunized against proteins vital to fertility.
Studies in male rats and rabbits have shown that this compound is effective as a reversible contraceptive and has few side effects. In a recent survey of about 1,800 men living in Edinburgh, Shanghai, Hong Kong, and Cape Town, South Africa, up to 83 percent said they would use a male contraceptive pill. Overall, pills were more acceptable than injectable or implantable contraceptives, the researchers reported in the March Human Reproduction . Acceptability isn't the only problem. Money and politics have always been issues in fertility research.