Male Birth Control Study Cut Short Due to Mild Side Effects

Men have never had the option to take a reversible pharmaceutical form of birth control, like women do, but there have certainly been ongoing efforts to make it a reality.

The pill was found to be the most popular form of contraceptive used by women ages 15 to 44 in the United States in 2013, according to the National Survey of Family Growth (NSFG). Men have never had the option to take a similar, reversible pharmaceutical form of birth control, but there have certainly been ongoing efforts to make it a reality. Researchers from across the globe came together to analyze an injectable hormonal contraceptive for men; and despite its confirmed efficacy, the trial was cut short.

Up until this point, only two small trials have provided results for a long-acting progestogen, norethisterone enanthate (NET-EN) with replacement doses of a long-acting androgen, testosterone undecanoate (TU). The results were encouraging, however, for being a safe and effective male contraceptive. With more data needed to assess outcomes, researchers conducted a trial with participants from 10 study centers.

The 320 male volunteers (ages 18 to 45) were all healthy and in monogamous relationships with females (ages 18 to 38). Their normal reproductive states were confirmed through sperm concentration, or sperm count, (at least 15 million/mL) or total sperm count (at least 39 million in each of two ejaculations). All of their partners had normal reproductive states as well.

During the suppression phase, the men were given 200 mg NET-EN (200 mg/mL) and 1000 mg TU (250 mg/mL) by two gluteal injections. They received the shots every eight weeks up to four times and the couples could use non-hormonal contraceptives. Once the men produced two consecutive semen samples within two weeks that had no more than one million/mL sperm concentration, they could move on to the efficacy phase of the study. The same shots continued every eight weeks for up to seven times, but this time, the couples were told to solely rely on the injections as a contraceptive.

By the end of 24 weeks, sperm concentration was one million/mL or less in 274 of the 320 men who had at least one injection. To put that into perspective, RESOLVE: The National Infertility Association determined that a sperm concentration less than 10 million/mL is poor — making the chances of pregnancy low.

Four pregnancies came about among the 266 men who went on to the efficacy phase of the trial — a rate of 1.57 per 100 participants. All of the women became pregnant before the 16-week mark of the study and three of the men had a concentration count of one million/mL or less.

The report published in The Journal of Clinical Endocrinology & Metabolism relieved one of the main concerns associated with a male contraceptive: “The cumulative reversibility of suppression of spermatogenesis after 52 weeks of recovery was 94.8 per 100 continuing users.”

A total of 1,491 adverse events (AEs) were reported among the participants, but 38.8% were not believed to be related to the injection. Twenty men discontinued the trial due to AEs even though 99% were classified as mild or moderate. The most concerning ones were mood changes, depression, pain at injection site, and increased libido. Acne, headache, and weight gain were also documented.

“Following the recommendation of an external safety review committee the recruitment and hormone injections were terminated early,” the researchers confirmed.

It was concluded that the injections were “relatively good” in terms of efficacy when compared to other reversible options for men. It’s unclear if or when this male contraceptive will be studied in the future.

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