Will male birth control pills ever work?

No one likes condoms; they're smelly, they dull the pleasures of sex, and someone has to slink them in the bin afterwards. And vasectomies? Who wants a surgeon with a surgical knife rummaging around down there?

But what other choices to do men have to ward against their partner's unplanned pregnancy?

"50% of the global population is missing a means to manage their reproductive health desires sufficiently," said Heather Vahdat, executive director of Male Contraceptive Initiative (MCI), a nonprofit.

This could all be changing soon. Drug developers are working on several different methods of male birth control and the results are looking promising.

"We need multiple products, and people are working on them," Vahdat told DW. "Some people want a pill everyday to know they're protected, but others want to take a pill as and when it's needed before sex."

Two types of male contraception

There are two main approaches to male contraception. One is a hormonal method which acts much like the pill for women — it is taken every day for several months or years to provide long-lasting contraception.

The other approach is an on-demand drug that can be taken right before sex to provide short-lasting contraception.

"What's pretty exciting now is work on the on-demand pills, but it's the hormonal products that are probably coming out soonest," Vahdat said.

Hormone-based male contraception

Both methods of birth control work by preventing sperm from developing, causing temporary infertility.

But don't let this scare you. The infertility really is temporary — fertility (spermatogenesis) returns to normal when you stop taking the contraceptive.

A clinical trial in 2022 showed a topical hormonal gel applied to a man's shoulder every day successfully prevented their partner/s from getting pregnant. The gel contained synthetic hormones, including testosterone, which sends a message to the brain to inhibit sperm production in the testes.

The gel lowered sperm production to 1 million sperm per milliliter, compared to the typical 15 to 200 million sperm per milliliter in healthy males. The birth control was reversible, as sperm levels returned to normal around 4 months after cessation of gel use.

But like the female pill, men needed to use the gel consistently for successful birth control.

"Spermatogenesis needs 7-10 weeks, which means a man has to take a hormone pill every day for 7-10 weeks before his sperm count is low enough for him to be essentially infertile. Then he has to take it continuously. But if he wants to stop, it takes 7-10 weeks for fertility to come back again," Jochen Buck, a professor of pharmacology at the Weill Cornell Graduate School of Medical Sciences in the US, told DW.

Non-hormonal male birth control

Non-hormonal contraceptive medications act in a similar way, but rather than altering hormonal signaling, they target specific molecular triggers of spermatogenesis.

Gossypol, a substance extracted from the cotton plant, is one such non-hormonal drug that provokes infertility in men by inhibiting spermatogenesis. Trials show the drug works, but perhaps too well, as it appears to lack reversibility in over 20% of subjects in trials.

But Buck and his colleagues are working on more promising drug candidates.

"Sperm is made in the testes," explained Buck. "Upon ejaculation they are mixed with semen fluid, which contains a signal to kickstart sperm into moving and searching. Without this they would never be able to leave the vagina to fertilize the egg."

Buck was one of the scientists who found the on-switch: adenylyl cyclase. He has since developed a drug that inhibits adenylyl cyclase and is testing its effects on birth control.

A different kind of pre-sex pill

A recent study published in the journal Nature Communications showed a different male contraceptive method: The team of US and German researchers found that the contraceptive they tested really did hold sperm back in the testicles — at least in mice.

"We gave a single dose of the drug that blocks adenylyl cyclase to male mice 30 minutes before mating and found it rendered them infertile for several hours," said Buck, who led the study.

This is a game changer for male birth control. It also offers a wildly different approach to contraception as it's on demand. Men could theoretically take a single dose of the drug 30 minutes before having sex, and it would last throughout the night before fertility resumes in the morning. But so far, it has only proven successful in animals. 

Are male contraceptives safe?

Many men would experience similar side effects women experience when taking the female pill.

"The hormonal approaches to male contraceptives have the risk of testosterone administration, so mood effects, impact on libido, weight gain (mostly muscle), reduction in HDL (good) cholesterol and night sweats," said John K. Amory, a male reproductive health researcher at the University of Washington in the US.

According to Amory, men using hormonal male contraception could also be banned from sports that test for the administration of steroid hormones for doping.

The side effects are partly what's causing hold-ups in male contraceptive development — promising trials have been stopped earlyafter participants reported adverse side effects.

Trials are working to address these safety concerns, but it's unclear when the contraceptives will be deemed safe enough to become commercially available.

As for Buck's on-demand drug, it's too early to say. His study showed that mice given the on-demand pill were fertile again a few days later, but this says little about other possible side effects, or how men will tolerate the drug in clinical trials.

There is still much work to be done improving the chemical properties of the drug before strict safety and efficacy tests in humans can take place. All this could take five to 15 years. It's unclear when on-demand pills will become available on the market.

Until then, best to stick to condoms, preferably in France — where they're free!

Edited by: Carla Bleiker