While women can choose from a number of birth control methods, men have few options to control their own fertility.
Available methods for men include condoms, vasectomies and withdrawal.
Better birth control options are needed for men. In 2012, 40% of all pregnancies worldwide were unintended, according to the Guttmacher Institute.
Now men can take birth control shots to prevent pregnancy in their female partners, according to a new study published in the Journal of Clinical Endocrinology & Metabolism.
In the study, researchers tested the safety and effectiveness of injectable contraceptives in 320 healthy men ages 18 to 45.
The participants had all been in monogamous relationships with female partners between the ages of 18 and 38 for at least a year.
The men underwent testing to ensure they had a normal sperm count at the start of the study.
The men received medical injections for up to 26 weeks to suppress their sperm counts. Healthcare professionals gave the men two injections every eight weeks.
Participants initially provided semen samples after 8 and 12 weeks in the suppression phase and then every 2 weeks until they met the criteria for the next phase.
During this time, the couples were instructed to use other non-hormonal birth control methods.
Once a participant’s sperm count was lowered to less than 1 million/ml in two consecutive tests, the couple was asked to rely on the injections for birth control.
During this period, the men continued to receive injections every eight weeks for up to 56 weeks.
Participants 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.
Researchers found that the hormones were effective in reducing the sperm count to 1 million/ml or less within 24 weeks in 274 of the participants.
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.
Researchers stopped enrolling new participants in the study in 2011 due to the rate of adverse events, particularly depression and other mood disorders, reported by the participants.
The men reported side effects including injection site pain, muscle pain, increased libido and acne. Twenty men dropped out of the study due to side effects.
Despite the adverse effects, more than 75% of participants reported being willing to use this method of contraception at the conclusion of the trial.
Researchers are still working to perfect the combination of hormonal contraceptives to reduce the risk of mild to moderate side effects, including depression and other mood disorders.
Citation: Behre HM, et al. (2016). Efficacy and Safety of an Injectable Combination Hormonal Contraceptive for Men. Journal of Clinical Endocrinology & Metabolism, published online. DOI: http://dx.doi.org/10.1210/jc.2016-2141.
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