OCT 29, 2016 7:57 AM PDT

Male Birth Control Works, But Many Side Effects for Now

The male birth control shot is effective, researchers say. But, there’s a big caveat to this claim – researchers still have to work on reducing the numerous side effects before the shot can become a reality.

In a phase II clinical study, researchers tested the efficacy of shot containing two hormones: a form of testosterone known as testosterone undecanoate, and a form of progestogen known as norethisterone enanthate (NET-EN). They reported the contraceptive was nearly 96 percent effective in preventing unwanted pregnancy. However, the trial was halted prematurely because the men were reporting high rates of side effects, including depression and other mood disorders.
"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," said Mario Philip Reyes Festin, who co-authored the study. "Our findings confirmed the efficacy of this contraceptive method previously seen in small studies."
While women have a range of contraceptive methods and brands to try, options for male contraceptives have been limited to condoms or the withdrawal method during sex. These methods are prone to error, leading to ineffectiveness at preventing pregnancy. The third option is a vasectomy, which, although highly effective, is invasive, costly, and may be permanent. A hormone shot to reduce sperm count could be the answer for couples everywhere.
In the study, healthcare professionals administered hormone shots to 320 healthy men whose ages ranged from 18 to 45. After the suppression phase was over and the men’s sperm count was sufficiently lowered (to less than 1 million per milliliter in two consecutive tests), the participants were asked to rely on the hormone shot as their primary birth control method. This efficacy phase was supported with ongoing hormone shots, which were given every 8 weeks up to 56 weeks.
During the efficacy phase, only 4 pregnancies occurred. This is highly comparable to the effectiveness of female birth control pills.

 But, preventing unwanted pregnancies via the male hormone shot came at a price – nearly 1,500 adverse events were reported for the group. These ranged from injection site pain to acne, to changes in libido, to mood changes and depression. The side effects lead to 20 men dropping out of the study. Of note, despite these side effects, over 75 percent of the men were willing to use the shot as a form of contraceptive.
Overall, the study offers tantalizing hope of a male birth control shot. But, as the researchers concede, "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.” Festin added, "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."

Additional sources: Science Daily
About the Author
Doctorate (PhD)
I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at TheGeneTwist.com.
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