Could an on-demand contraceptive pill for men one day be a reality?

Research on mice suggests it may be possible to develop a contraceptive pill that men can take shortly before sex to make them temporarily infertile.

What is the research about?

A new approach to developing a contraceptive pill for men. The US-funded study ran tests on male mice just before they mated to try out a new drug that temporarily stops sperm from moving.

Why is this research important?

Currently, men only have two contraceptive options: external condoms (also known as male condoms) and vasectomy.

Women have more options to prevent pregnancy. This, and the fact that it is women who get pregnant, means women are often considered responsible for managing contraception. A male pill could make things more equal.

Researchers have been trying to develop a male contraceptive pill for years. Most studies have focused on developing drugs that impact sperm development. But most of these contraceptives aren’t considered good enough to develop further because they have to be taken for months before they work, and it also takes months for fertility to return after use. Developing a male contraceptive drug that works almost instantly and wears off quickly could be a game changer.

What did they find out?

Researchers developed a drug called a soluble adenylyl cyclase (sAC) inhibitor. sAC is an enzyme present in almost every cell in the body. In men, it is essential for making sperm move. The sAC inhibitor temporarily stops sperm from moving.

In humans, pregnancy happens when sperm moves from the vagina across the cervix into the uterus to fertilise an egg. But if sperm is unable to move out of the vagina because it is temporarily immobile it will not be able to survive, and pregnancy will be prevented.

Researchers used the sAC inhibitor on male mice (oral doses or injections). Thirty minutes after receiving a single dose, the mice’s sperm stop moving.

The sAC inhibitor did not affect mating behaviour, and the mice were able to ejaculate semen (the fluid containing sperm) as normal. But they were not able to impregnate the female mice they were mating with.

The effects lasted for around three hours. The mice were fully fertile again the next day.

Once fertility returned, the male mice mated successfully. No pregnancy complications were detected and the mice’s offspring were healthy.

What does this mean for sexual and reproductive health services?

This new approach shows promise for one day developing an on-demand, reversible contraceptive for men.

But this research is still in the early stages. Other tests on animals, such as rabbits, will need to happen before human trials using sAC inhibitors can begin.

The sAC inhibitor does not involve any hormones, so it is likely to have fewer side effects than hormonal contraceptives. This could be another selling point. But, like the female pill or injection, the sAC inhibitor does not protect against sexually transmitted infections, so condoms would still need to be used.

Until there are more contraceptive options for men, it is important to speak to men and women about the need for shared responsibility when it comes to family planning and preventing pregnancy.