A contraceptive injection for men has been developed successfully, it has been announced.
However, the World Health Organisation (WHO), which was one of the sponsors of the research, said further studies are needed to balance efficacy and safety, after some men reported depression and other mood disorders among the side effects.
The study, which is published in the Journal of Clinical Endocrinology & Metabolism, was a phase II single arm, multi-centre study tested the safety and effectiveness of injectable contraceptives in 320 healthy men ages 18 to 45, all of whom had a normal sperm count when the research began.
They had two injections every eight weeks of 200 milligrams of norethisterone enanthate (NET-EN) and 1,000 milligrams of testosterone undecanoate (TU) for up to 26 weeks to suppress their sperm counts.
Participants provided semen samples after eight and 12 weeks in the suppression phase and then every two weeks until they met the criteria for the next phase.
The men and their partners were instructed to use other non-hormonal birth control methods until their sperm count was less than 1 million/ml in two consecutive tests.
During this efficacy phase, the men received injections every eight weeks for up to 56 weeks and they provided semen samples every eight weeks to ensure their sperm counts stayed low. Once the participants stopped receiving the injections, they were monitored to see how quickly their sperm counts recovered.
The hormones were effective in reducing the sperm count to 1 million/ml or less within 24 weeks in 274 of the participants and the contraceptive method was effective in nearly 96% of continuing users. Only four pregnancies occurred among the men’s partners during the efficacy phase of the study.
Side effects included injection site pain, muscle pain, increased libido and acne, but particularly depression and mood disorders, and 20 men dropped out of the study due to side effects.
Dr Philip Reyes Festin, of WHO and one of the study authors, said: “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. 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.”
Efficacy and Safety of an Injectable Combination Hormonal Contraceptive for Men. Journal of Clinical Endocrinology & Metabolism 27 October 2016.
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