Could a Male Birth Control Shot Be on the Horizon?

Although men generally have fewer options for controlling their fertility than women, an investigational hormone shot could provide male patients with a new way to help prevent pregnancy in their female partners.

A recent study published in the Journal of Clinical Endocrinology & Metabolism evaluated the safety and efficacy of this potential contraceptive by administering it to 320 healthy men aged 18 to 45 years; all of the participants had been in monogamous relationships with female partners between the ages of 18 and 38 for at least a year, and they all had normal sperm counts at the start of the trial.

The drug, a combination of 200 mg of a long-acting progestogen (norethisterone enanthate) and 1000 mg of a long-acting androgen (testosterone undecanoate), is injected every 8 weeks in order to suppress a patient’s sperm count. The injection initially appeared to work as designed, reducing the sperm counts of 274 of the participants to 1 million/ml or less within 24 weeks.

When their sperm counts reached these levels, the men and their partners were asked to rely on the shot as their only form of birth control. At the end of the study, the injection was found to be 96% effective at preventing pregnancy, as only 4 of the continuing users’ partners became pregnant during the 56-week trial period.

Adverse events reported by the trial participants include depression and other mood disorders, injection site pain, muscle pain, acne, and increased libido. Twenty men dropped out of the study as a result of these side effects, and the study stopped enrolling new patients after 3% of participants were found to have developed depression.

However, the researchers concluded that nearly 39% of reported adverse events were unrelated to the drug’s use, including one death by suicide. Additionally, 75% of participants expressed their willingness to use the injection as a form of birth control despite the potential adverse effects.

Although the study’s authors found the results to be promising, they nevertheless emphasized that further efforts are required to minimize the adverse events linked to the use of hormonal contraceptives in men.

“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,” said study author Mario Philip Reyes Festin, MD, in a press release. “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.”