• More than 75 per cent of men who took part in the trial said they would happily use the contraceptive injection as a means of birth control. (Westend61/Getty Images)Source: Westend61/Getty Images
The trial was discontinued because a small percentage of men experienced side-effects such as mood swings, depression and muscle pain.
By
Alyssa Braithwaite

31 Oct 2016 - 11:58 AM  UPDATED 31 Oct 2016 - 12:26 PM

A groundbreaking trial of a male contraceptive injection has been abandoned after about six per cent of men experienced side effects, including depression, muscle pain, mood swings, acne and heightened libido, according to a new study.

The trial involved 320 men who were given a hormone injection of progestogen, which blocks sperm production by acting on the brain's pituitary gland, and testosterone, which counterbalances the resulting reduction in male hormones.

The study documenting the trial results, published in the Journal of Clinical Endocrinology & Metabolism by the Endocrine Society today, shows that the injection was 96 per cent effective at preventing pregnancies among the couples taking part in the year-long trial. There were only four pregnancies out of the 266 couples.

According to the study, 75 per cent of men involved in the trial said they were willing to continue using the injection for birth control.

The resulting pregnancy rate of 1.57 per 100 users is comparable to that of the combined contraceptive pill, which has a rate of less than 1 pregnancy per 100 women who use it.

According to the study, 75 per cent of men involved in the trial said they were willing to continue using the injection for birth control.

However, the trial was discontinued after an external panel of reviewers concluded that the risks to participants outweighed the potential benefits, and said more work was needed to address the treatment's reported side effects. Of the 320 men participating in the trial, 20 dropped out because of  the side effects.   

There was one case of depression, one intentional paracetamol overdose, and one case of an irregular heart rate – all judged as being possibly related to the injection.

"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 co-author of the paper, Mario Festin, from the World Health Organisation.

“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.”

The study looked at men aged 18-45 who had been in monogamous relationships for at least one year and were given injections every two months.

Their sperm counts were reduced from a normal level of over 15 million per millilitre to under one million per millilitre.   

Once they stopped having the injections, the participants were monitored to see how quickly their sperm counts recovered.

Eight men had not recovered their normal sperm counts one year after the completion of the study.

There was one case of depression, one intentional paracetamol overdose, and one case of an irregular heart rate – all judged as being possibly related to the injection.

The contraceptive pill for women was first launched in 1962, and there has been  no progress in male contraceptives for more than 40 years.

Leading fertility expert Allan Pacey, from the University of Sheffield, said the evidence showed the injections to be “extremely effective” but he was concerned about the side effects.

"For a male contraceptive to be accepted by men (or women) then it has to be well tolerated and not cause further problems," Pacey states in a statement accompanying the study.

"For me, this is the major concern of this study."

But he also noted that three out of four men said they would be willing to use the injection for contraception again, "so perhaps the side-effects weren't all that bad after all." 

Contraception: How much choice do women actually have?
There's so much more to contraception than just taking the pill. Jo Hartley explores how much contraceptive choice women have.
Birth control's troubling myths
Nearly a third of women are misinformed about the most effective forms of contraceptives, a new report finds.
Can you blame your birth control for your insomnia?
Here's how hormones - both synthetic and natural - affect your sleep.