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By Maggie Fox
The National Institutes of Health is looking for a few good men to try out a new birth control gel for men.
The gel, rubbed into the shoulders daily, gradually brings down sperm counts so that men can not make a woman pregnant. The National Institute of Child Health and Human Development (NICHD), part of the NIH, plans to register about 400 couples at sites around the world to test how well the gel works to prevent pregnancy, and check out how well people like it and whether men will use it as directed.
"This is the first time that people use it as part of a couple to test for effectiveness," said Diana Blithe, head of NICHD's Contraceptive Development Program.
The gel formulation, called NES / T, includes a progestin-containing compound called Seedterone acetate, which is made under the brand name Nestorone, along with a testosterone dose.
"It is applied to the back and shoulders and absorbed through the skin. The progestin blocks the natural testosterone production in the tests, reducing the sperm production to low or nonexistent levels, "the NICHD said in a statement.
It is formulated as a gel because Nestorone does not get absorbed by the body when it is taken orally, and testosterone does not stay in the body for a full day when taken as a pill. Both hormones last longer and work better when dosed through the skin.
There is no commercial male hormonal contraceptive on the US market now. All have to choose from are condoms or vasectomy.
"Worldwide, 85 million pregnancies per year are unplanned, contributing to a higher incidence of adverse health outcomes for women and infants," said the Population Council, which developed the product, said in a statement.
Nestorone, combined with the hormone estradiol, is also used as a female contraceptive. A product was approved by the US Food and Drug Administration in August as part of a vaginal ring for women to use as birth control.
How can the same hormone work as a contraceptive in both men and women? It's because many common hormones have similar chemical structures, Blithe said.
In men, the hormone tricks the body into thinking it can stop making sperm. In women, it mimics pregnancy and tricks the body into thinking it can stop making eggs. "The male has very low levels of progesterone normally. Now they are exposed to a high amount, and that tells the tests, 'oh there is a lot of steroid around so I do not need to do more now,' "Blithe said.
Giving back some testosterone along with the Nestorone stops unwanted side effects such as low libido and muscle loss, Blithe said.
One question is how effective the treatment will be. Different birth control methods have different efficacies.
"If we are talking about a daily pill in women, if they use it perfectly, the failure rate is extremely low," Blithe said. "In typical use the failure rate is 7 percent. With condoms, if they are perfectly used, the failure rate is low but in typical use the failure rate is 12 percent. "
In theory, one could forget to use the gel for a day with no consequences. "If they stop using it for three, four, or five days, then it will not work the way it is supposed to," Blithe said.
"Do you think they'll use it? Certainly, they are able to use it and they are willing to use it. But people are human and people forget. "