Side Effects Sideline Promising Male Birth Control Shot


A new male contraceptive method has proven highly effective at reducing pregnancy in female partners, yet consumers may not find it on the market for awhile after the study was shuttered over safety concerns.

Appearing in The Journal of Clinical Endocrinology & Metabolism, the research study assessed the impact of hormonal injections on men and rates of pregnancy for couples that had regular sexual intercourse.

Studying more than 300 men between 18 and 45 who are in monogamous relationships, the researchers administered a combination injection of testosterone and progestin in the male participants every two months. They instructed the couples to have sex twice per week.

After months of monitoring, the researchers found a 95.9 percent success rate in avoiding unwanted pregnancies.

“The contraceptive efficacy is high, especially when compared with other reversible methods available for men, and is comparable with the efficacy of female oral contraceptive methods, as typically used,” states the study, which was co-sponsored by the United Nations.

The injections work by suppressing sperm production, which results from the body no longer generating testosterone on its own following the testosterone shot. The result is “a near-complete suppression of spermatogenesis,” or the complex process behind sperm production, and ultimately and minimized sperm concentrations.

The new method, interrupted

Over the past 50 years, many options, including hormonal methods, have been available to women, and about 75 percent of married women in North America report using some form of contraception. For men, it’s an entirely different picture. “Options for men to control their own fertility remain limited to withdrawal, condoms and sterilization,” says the study.

Yet, safety concerns led researchers to put the brakes on the new method under study. “The risks to the study participants outweighed the potential benefits to the study participants,” states the study.

Some male participants reported mood changes, depression, increased libido and pain at the injection site. “The frequency of reported moderate and severe mood disorders, including depression, heightens awareness of the potential behavioral effects that this combination regimen may have on some individuals,” says the study.

The effect of hormone-changing contraceptives is not new to the medical community, as previous studies have documented the potentially harmful effects on women taking these types of contraceptives.

Yet despite the stalled study, most men found the hormonal injections tolerable and would opt to use them. “Male participants and their partners found this combination to be highly acceptable at the end of the trial, even after being made aware of the early termination of the study intervention. More than 75 percent reported being at least satisfied with the method and willing to use this method if available, which supports further development of this approach,” states the study.

While couples wait for a male contraceptive method that can help ease the burden on women, similar studies are expected to churn out results in the meantime after such a promising start. “Such trials are urgently required to enable full assessment of the potential of this approach to new contraceptive product development,” state the researchers.