No male hormonal contraceptive is ready for clinical use. Most trials were small exploratory studies. Their power to detect important differences was limited and their results imprecise. In addition, assessment of azoospermia can vary by sensitivity of the method used. Future trials need more attention to the methodological requirements for RCTs. More trials with adequate power would also be helpful.
Male hormonal contraception: a double-blind, placebo-controlled study.
This study was performed to assess spermatogenesis suppression and safety of a new combination of an etonogestrel (ENG) implant combined with testosterone undecanoate (TU) injections for male contraception. This is the first large placebo-controlled study for male hormonal contraception. DESIGN AND STUDY SUBJECTS: In this double-blind, multicenter study, we randomly assigned 354 healthy men to receive either a low- or high-release ENG implant sc combined with im TU injections (750 mg every 10 or 12 wk or 1000 mg every 12 wk) or placebo implant and injections. Treatment duration was 42 or 44 wk and posttreatment follow-up at least 24 wk.
                Overall, spermatogenesis was suppressed to 1 million/ml or less at wk 16 in 89% of men, with approximately 94% in two high-release ENG groups. Suppression was maintained up to the end of the treatment period in 91% of men. For all men who completed the treatment period, 3% never achieved 1 million/ml or less. Median recovery time to a sperm concentration above 20 million/ml was 15 wk (mean 17 wk, 95% confidence interval 16-18 wk). Treatment was well tolerated. As compared with the placebo group, more men in the active treatment groups reported adverse events such as weight gain, mood changes, acne, sweating, or libido change. For both spermatogenesis suppression and safety, differences were small between the active treatment groups.
                The combination of an ENG implant with TU injections is a well-tolerated male hormonal method, providing effective and reversible suppression of spermatogenesis. Although the results are good, there is still room for improvement, possibly by adjusting the dose regimen or changing the mode of application.