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A couple stands close to one another on a bridge at sunset.
Reuters/Sergei Karpukhin
We won’t be sharing the burden of birth control just yet.
MAN UP

There’s a birth control shot for men that works—but they can’t seem to handle the side effects

By Katherine Ellen Foley

It takes two to tango, but the burden of birth control falls largely on women.

Although men can wear condoms to prevent both pregnancy and sexually transmitted infections, rubbers have a failure rate of 18% when used typically for a year, and reportedly detract from some of the physical sensations of sex. So in most committed relationships, women take on the charge of birth control.

In 2015, 64% of coupled women globally (pdf) were using some form of chemical birth control. These methods—whether a hormonal pill, shot, or implantable device—all work fairly well at preventing pregnancy, but none are perfect. The pill is the least invasive option—but it still must be taken at the same time every day for it to be fully effective, and has been linked to weight gain, acne, breast tenderness, decreased libido, and, most recently, depression.

Although these side effects don’t occur in all women, wouldn’t it be great if men could alleviate this discomfort for their partners in these cases?

Turns out they can! Scientists have created a hormonal injection for men that works just about as well as the pill does for women. One injection to the rear every eight weeks works about 96% of the time to prevent pregnancies. Unfortunately, though, in a clinical trial of over 300 men published (pdf) Oct. 27, most of the men didn’t complete the full duration of the study because of side effects, including mild to moderate muscle pain, mood disorders, acne, and increased libido.

Yep. Wouldn’t want that tradeoff for reversible birth control.

The team of researchers from all over the world, including Germany, Italy, India, Australia, and the UK, injected 320 men for the study with two hormones: one essentially shut down the generation of new sperm, and the other was testosterone to make sure the men “feel OK,” Richard Anderson, a reproductive specialist at the University of Edinburgh and author of the paper, told the Guardian.

All of the men were in committed relationships with women that included “a coital frequency of twice [per] week on average” and who did not want children, but were okay with a relatively low, although unknown, risk of it. (In birth control studies, there can’t really be a control group that gets placebos.)

First, the researchers looked at the men’s semen to see if their sperm count had been reduced. They received injections every two months for an eight-month period, during which they only used non-hormonal contraception—like condoms—with their partners. Next, they stopped using all other kinds of birth control, while the men continued to receive injections every two months for 14 months.

Part of the way through the study, though, 20 men dropped out because of the side effects. Some experienced changes in mood, increased libido, and acne—pretty similar to what women have suffered while taking the pill for years. Of the 1,491 total complaints of side effects made during the study, researchers ruled out 39% as being unrelated to the injections themselves.

However, a review panel ruled that the study should be discontinued “for safety reasons.” Although they followed up with men to regulate their sperm recovery, they stopped receiving injections and recruiting others. At that time, only 111 men had completed the full duration of the trial.

Scientists still think that these early results mean the quest for male birth control should continue, and plan on conducting future studies once they can tweak the doses of hormones to try to eliminate some of these side effects. It was, after all, very effective at preventing pregnancy: only four couples became pregnant from 266 men who made it through at least some of the phase of the study. And, despite the side effects, 75% of the men who completed the trial said they’d be willing to keep it up as a form of birth control.

Correction: An earlier version of this article misstated condoms efficacy.