It blocks gonadotropin signaling and testosterone production in the testes. When capsules ranging in dose from 100 mg to 400 mg were given once daily to 100 men in a randomized, placebo controlled trial, the drop in testosterone was more than sufficient to block sperm production. Testosterone levels jumped back up to normal after the end of the 28-day trial, all without inducing liver toxicity or other serious problems.
“We are very excited [about] the results. It’s a big step forward in the development of the male pill. Our last great advance in male contraception was over 300 years ago with the development of the condom,” said senior investigator, PhD, head of the division of metabolism, endocrinology, and nutrition at the University of Washington, Seattle.