A new male birth control pill passed safety and tolerance tests when healthy men used it daily for one month and produced hormonal responses consistent with effective contraception, according to researchers from two institutes examining the drug.
The oral contraceptive is called 11-beta-MNTDC. It is a modified testosterone that has the combined effects of a male hormone (androgen) and a progesterone, said study investigator Christina Wang.
"Our results show that this pill, which combines two hormonal activities in one, will reduce semen production while maintaining libido," said Wang.
The study was conducted in 40 healthy men at the University of Washington in Seattle, USA. Ten participants in the study received a randomized placebo or placebo capsule. The other 30 men received 11-beta-MNTDC in one of two doses. 14 men received 200 milligrams or mg and 16 took the 400 mg dose. Individuals received the drug or placebo once daily with food for 28 days.
Among those taking 11-beta-MNTDC, the median level of circulating testosterone fell as low as in androgen deficiency, but the participants were reported not to have any serious side effects. Wang reported that the side effects of the drugs were few, mild and included fatigue, acne or headache in four to six men. Five men reported slightly reduced sexual momentum and two men described mild erectile dysfunction, but sexual activity did not decrease, he said. In addition, no participant stopped taking the drug because of side effects and everyone passed safety tests.
The effects of low testosterone were minimal, according to co-researcher Stephanie Page, because "11-beta-MNTDC mimics testosterone through the rest of the body but is not sufficiently concentrated in the testis to support sperm production."
The levels of the two hormones required for sperm production decreased significantly compared to placebo, according to the researchers. The effects of the drug were reversible after cessation of treatment, Wang noted.
Because the drug would require at least three 60 to 90 days to affect semen production, 28 days of treatment is too short to see optimal sperm suppression, Wang explained. They are planning longer studies, and if the drug is effective, it will go ahead with larger studies and then test for sexually active couples.
Wang reported that most men are open to using this type of male birth control. He referred to a 9,000-man multinational survey published in Human Reproduction in February 2005 that found that 55% of men in stable relationships want to test new, hormonal male contraceptive methods if they are reversible.