Several methods of male contraception are currently under investigation. The one that has gotten the most attention lately uses hormonal gels that men rub into the skin on their shoulders daily. The gels contain testosterone and a synthetic hormone called Nestorone that is similar to progesterone. In a study at UCLA, 56 men tested this new method for 20 weeks. While using the combination of hormones, their sperm counts dropped dramatically – from about 15 million per cubic milliliter of ejaculate to 1 million or less, a level that is compatible with very low pregnancy rates. The researchers reported that most of the men made no detectable sperm during the study. Another group of men received a testosterone gel and a placebo. In this group, sperm counts dropped below one million in only 23 percent of the subjects. None of the men in the trial knew whether they were getting the hormonal combination or the testosterone plus placebo.
This approach to contraception works by shutting down processes in the brain that regulate sperm manufacture by the testes. The treatment is reversible; sperm counts returned to normal about 12 weeks after the men stopped using the hormonal gels. The only side effect was acne, which developed in about one-fifth of the participants. While this study is promising, larger trials of a single gel that combines both hormones will be needed before it can be submitted for FDA approval.
A number of other approaches are being tested. These include:
- Researchers in Scotland have detected a gene - Katnal1 - that plays a key role in the maturation of sperm. It might be possible to develop a non-hormonal pill that would target Katnal1 and block this process.
- Researchers in India are working on a male contraceptive that requires injecting a polymer called Vasalgel into the scrotum, where it solidifies, blocking the movement of sperm. The procedure is reversible with another injection that flushes out the polymer. Fertility returns in two to three months.
- Also in development is the use of ultrasound to heat the scrotum in order to reduce sperm production. In studies with dogs, this method resulted in permanent contraception, but the effects were only temporary in monkeys.
Despite this research, no male contraceptive is likely to become available any time soon. For now, men should use condoms, undergo vasectomy, or rely on women’s contraceptive use to prevent unwanted pregnancies.
Andrew Weil, M.D.