NEW YORK (CBSNewYork) – The first clinical trial is underway to test a new male contraceptive that could be a game changer for preventing pregnancy.

“(It’s) a combination of two horomones: Progestin, which is the typical horomone that is found in female contraceptive pills, which they put in there to suppress sperm production, to trick the body, and testosterone, which is the male sex horomone so that there’s normal circulating levels of testosterone that men don’t lose their libido or sexual function or have any changes in mood,” said CBS News medical contributor Dr. Tara Narula.

The National Institutes of Health is enrolling about 420 couples to use an experimental gel that has been in development for more than 10 years.

If proven effective, it would be the first hormonal birth control for men.

The gel is applied to the back and shoulders. Researchers found that testosterone, once absorbed through the skin, stays in the system longer than testosterone taken in pill form does.

Male volunteers will use the gel every day for four to 12 weeks.

“Researchers are going to monitor their sperm count over a couple months,” said Narula. “When the sperm count has declined enough they’re going to tell the couples only use the gel as your form of oral contraception and then watch a year.”

Dr. Stephanie Page, who is running the test at the University of Washington, says says the trial is not without risk.

“We’ve done everything we can to minimize the possibility in this study, but we talk to people about the risks involved and make sure that they understand pregnancy is a possibility,” said Page.

The men will then remain in the study for an additional 24 weeks once they’ve stopped taking the gel to see if their sperm count recovers.

Page has also been testing a male birth control pill, but up until now the only form of male birth control has been condoms and vasectomy.

Unlike for women, the birth control pill for men has taken much longer.

“It’s much more difficult to suppress the development 150 million sperm per day than it is to suppress one or two eggs per month,” said Page.