Side effects halt trials of game-changing male contraceptives
An experimental birth control injection for men was found to be 96% effective in a recent trial involving 320 men over a period that lasted more than a year. However, the trials were briefly ended as some of the participants reported experiencing side effects due to the treatment.
The hormone-based contraceptive injection is designed to lower sperm counts by acting on the brain’s pituitary gland.
The injections contained a long-acting form of progestogen, a hormone that has the effect of blocking sperm production controlled by the pituitary gland. Testosterone was added to counter-balance reductions in levels of the male hormone resulting from the treatment.
After an initial period during which couples used both the injections and other birth control methods, the men entered the study’s “efficacy phase” and relied on the jabs alone.
Throughout the efficacy phase, which lasted up to a year, the men were given injections every two months. During this time four pregnancies occurred among the partners of 266 participants – a rate of 1.57 per 100 users. The combined contraceptive pill, for comparison, has a rate of less than 1 pregnancy per 100 women who use it.
Mario Festin, from the World Health Organization (WHO) said: “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.”
However, researchers said more work was needed to address the treatment’s reported side effects, which included depression and other mood disorders, muscle pain, acne and increased libido.
Twenty of the participants reported side effects, which included one case of depression, one intentional paracetamol overdose, and one case of an irregular heart rate, and eventually dropped out of the trial. This resulted in the trial ending earlier than planned as an external panel of reviewers concluded that the risks to the study participants outweighed the potential benefits.
Festin says more research is needed to advance the concept for wide commercial use. “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,” he added.
Still, more than 75% of the men who participated in the trial said they were satisfied with the injection and would continue to use it if it were available.
Chris Barratt, professor of reproductive medicine at the University of Dundee, said: “This is high-quality research from a very experienced group of investigators, and as there has been no progress in male contraceptives for 40-plus years this is a very significant and welcome development.”
