Birth Control Injections for Men May Prevent Pregnancy

The development of a hormonal contraceptive for men may help couples prevent pregnancy, study results published in the Journal of Clinical Endocrinology & Metabolism suggest.¹

While the number of birth control methods available to women has grown, those for men, including condoms, vasectomies, and withdrawal, remain limited.¹

In a prospective, phase 2, single-arm, multicenter study, researchers evaluated the safety and effectiveness of injectable contraceptives in 320 healthy men aged 18 to 45 years who were in monogamous relationships with women aged 18 to 38 years for at least 1 year. Neither the men nor women had fertility problems, and the men had normal sperm count at the beginning of the study.

For up to 26 weeks, men received intramuscular injections of 200 mg norethisterone enanthate and 1000 mg of testosterone undecanoate to suppress sperm count, receiving 2 injections every 8 weeks. Semen samples were analyzed after 8 and 12 weeks in the suppression phase, followed by every 2 weeks until they met criteria for the next phase. During this period, couples were told to use nonhormonal birth control methods. After sperm count was lowered to less than 1 million/mL in 2 consecutive tests, participants entered the efficacy phase, during which men continued to receive injections every 8 weeks for 56 weeks and the researchers asked that participants rely solely on injections for birth control. Semen samples were provided every 8 weeks to ensure that sperm counts remained down. After ceasing injections, participants were monitored to see how quickly sperm counts recovered.

During the suppression phase, injections suppressed sperm counts to 1 million/mL or less in 95.9 of 100 continuing users (95% CI, 92.8-97.9) of the 320 participants by 24 weeks.¹ During the efficacy phase of up to 56 weeks, the rate of pregnancies was 1.57 per 100 continuing users (95% CI, 0.59-4.14), with 4 occurring among the female partners of the 266 male participants.¹ After 52 weeks, receiving of sperm count was 94.8 per 100 continuing users (95% CI, 91.5-97.1).¹

“The study found it is possible to have a hormonal contraceptive for men that reduces the risk of unplanned pregnancies in the partners of men who use it,” study author Mario Philip Reyes Festin, MD, of the World Health Organization in Geneva, Switzerland, said in a press release.² “Our findings confirmed the efficacy of this contraceptive method previously seen in small studies.”

Despite these positive results, the rate of adverse events, which included acne, injection site pain, muscle pain, increased libido, and mood disorders like depression, was high enough to prompt researchers to stop enrolling new participants in 2011.¹

Of the 1491 reported adverse events, about 39% were unrelated to the contraceptive injections, according to the researchers, including 1 death by suicide.¹ Serious events that were deemed to be probably or possibly related to the study included 1 case of depression, 1 intentional overdose of acetaminophen, and 1 case of abnormally fast and irregular heartbeat that occurred after the participant stopped receiving injections.¹

Although 20 men discontinued the study due to these side effects, more than 75% remained willing to use this method of contraception after conclusion of the trial.¹

“More research is needed to advance this concept to the point that it can be made widely available to men as a method of contraception,” Dr Festin said.² “Although the injections were effective in reducing the rate of pregnancy, the combination of hormones needs to be studied more to consider a good balance between efficacy and safety.”

Disclosures: Robert I. McLachlan, PhD, is a Principal Research Fellow ofthe Australian National Health and Medical Research Council(1022327) and the Hudson Institute, which is supported by theVictorian Government’s Operational Infrastructure Scheme.The authors have nothing to disclose.

References

1. Behre HM, Zitzman M, Anderson RA, et al. Efficacy and safety of an injectable combination hormonal contraceptive for men. J Clin Endocrinol Metab. 2016 Oct 27. doi:10.1210/jc.2016-2141 [Epub ahead of print].
2. Male birth control shots prevent pregnancy [press release]. Washington, DC: Endocrine Society Newsroom; October 27, 2016. https://www.endocrine.org/news-room/current-press-releases/male-birth-control-shots-prevent-pregnancy. Accessed October 28, 2016.