U.S. government scientists will test an experimental birth control method for men, which would be a major advance in contraception and bring more equality to a family planning burden borne largely by women.

The study is being conducted by the National Institutes of Health and will involve 420 couples. The experimental treatment is a gel, applied to the back and shoulders, that combines two types of hormones to halt the production of sperm while maintaining the energy and libido benefits of testosterone.

“This gel would be the first user-controlled method of contraception for men since the introduction of the condom,” said Diana Blithe, chief of the contraceptive development program at the National Institute of Child Health and Human Development. “We hope it will be an acceptable form of contraception that couples will want to use.”

The gel is a mix of progestin and testosterone, and researchers will examine how successful the gel is at preventing pregnancies. People who rely on condoms have a 12 percent to 13 percent failure rate, while relying on hormone-based birth control pills fails about 7 percent of the time.

“There are some men who may like to control their own fertility, who may or may not be in a monogamous relationship,” said Blithe, who is an investigator for the trial, in a telephone interview. “This would be an option for them.”

A New Method?

Millions of women around the world use birth control, which has been around for decades as a reliable, relatively convenient form of contraception. While many women would likely want to maintain control over the contraceptive method used in a sexual encounter, some either can’t take the pill or prefer not to.

Blithe said that the limited options for men led several couples to reach out in advance of the study asking to participate. Earlier research in men alone shows that the approach reduces sperm production and that it rebounds after the gel is stopped, without causing serious side effects.

The NIH researchers crafted the gel with the Population Council, a nonprofit group that works on reproductive health issues. The Council helped develop RU486, or mifepristone, a pill that can be used to end an early pregnancy. Blithe said that if they gel for men is successful, a commercial partner would be found to help sell it.

Testosterone Levels

The drug is formulated as a gel since testosterone is cleared too quickly from the body when it’s taken as a pill. The progestin in the gel, called Nestorone, blocks the natural production of testosterone in the testes, where sperm is made. The testosterone replaces the hormone in the blood.

“You are cutting it off at the source, but replacing it everywhere else at a levels that keeps everything else functioning normally,” Blithe said, pointing out that testosterone levels in the testes are 50 times higher than the amount normally found in the blood.

The researchers will track men for four to 12 weeks to ensure their sperm production has fallen significantly enough to prevent conception, with women using an alternative form of birth control just in case. After that, couples will rely on the gel alone. If the results are positive, another larger trial will be needed before the product could get approval.