After years of intrigue, researchers are celebrating "a major step forward" for the male birth control pill. A month-long clinical trial shows a once-daily male pill is safe and effective at suppressing the hormones needed for sperm production, and has no negative effect on sex drive, according to researchers who presented their findings Sunday at the Endocrine Society's annual conference in Chicago, per the Telegraph. The hormone pill, dimethandrolone undecanoate (DMAU), overcomes issues that plagued earlier versions of the male contraceptive. In addition to concerns about how low testosterone would affect sex drive, researchers feared the pill would need to be taken twice daily, given the speed that hormones clear the male body, reports the Guardian. DMAU, however, contains fatty acid undecanoate which is believed to slow the clearance.
Some 100 men aged 18 to 50 received a placebo or varying doses (100mg, 200mg, or 400mg) of the pill, which contains an androgen and a progestin and must be taken with food. After 28 days, all pill-popping patients saw low testosterone levels, while patients given the 400mg dose saw a "marked suppression" in testosterone and two other hormones needed for sperm production, reports the Telegraph. Patients also saw mild weight gain and a slight drop in HDL or "good cholesterol" levels, per NBC News. But "very few subjects reported symptoms consistent with testosterone deficiency or excess," and liver and kidney function remained healthy, senior researcher Stephanie Page says in a release. "These promising results are unprecedented in the development of a prototype male pill." Research will now focus on effects over longer periods. (Another male pill might leave hormones alone.)