The most promising combination currently in development for a male contraceptive pill involves either the synthetic hormone desogestrel, or gestagen, along with testosterone. During trials, sperm counts have been found to drop to zero, making the pill more effective than almost any other form of contraception.
It carries almost no side effects, with only minor weight gain reported in a small number of men for the desogestrel version. There have been reports of reversible shrinkage of the testicles in the gestagen combination.
The biggest drawback to this method is the need to take a daily pill. Research is underway on an implanted version, as well as a cream and patch.
Cost is expected to be equivalent to that of condoms. The results are reversible, but the drop in sperm count may take from a few weeks to four months to occur.