Reversible Male Birth Control Vasalgel Shown to Prevent Pregnancy in Rabbits

Vasagel, a new non-hormonal, reversible male contraceptive proved highly effective in a recent rabbit study. REUTERS/Ina Fassbender

Updated | When it comes to preventing unwanted pregnancy, much of the onus is still on women. Sure there are condoms and vasectomies, but all long-acting, reversible forms of birth control are made for women—from patches to intrauterine devices to hormone pills. Despite these contraceptives 40 percent—85 million—of all pregnancies worldwide are not planned, according to the Guttmacher Institute, a research organization for reproductive and sexual health. This is why experts have long been looking for a way for men to play an active role in birth control, while still maintaining fertility.

The good news is we may be on the cusp of a breakthrough. It's called Vasalgel, and it's a non-hormonal and reversible form of male birth control. On Tuesday, researchers published their findings on March 29 in Basic and Clinical Andrology, a medical journal. Naturally, they chose rabbits as their first study cohort, and found the injectable contraceptive was nearly 100 percent effective.

Here's how it works: Vasalgel is a liquid-based injection placed into the vas deferens, the duct that carries sperm from the testes to semen. The gel is made from polymer called styrene-alt-maleic acid (SMA), which is dissolved in dimethyl sulfoxide, a chemical solvent that is also happens to be used for treating painful bladder syndrome. The combination of the two substances function as a way to block semen from entering into ejaculant, and causes temporarily infertility.

For the study researchers tested two different formulations of the gel, and injected it into the vas deferens of 12 male rabbits. Next, they analyzed semen samples and found 11 of the rabbits had no detectable sperm. The last rabbit had low sperm count that quickly went to zero. They also found the Vasalgel stayed effective for 12 months and didn't appear to cause any harm to the animals.

The researchers also tested the removal of the implant by simply flushing it away with sodium bicarbonate solution. The process proved effective in all seven rabbits tested, and sperm rapidly returned to the semen samples without any harm.

The next step is a Vasalgel clinical trial on men, which researchers have planned for late 2016. The project is spearheaded by the Parsemus Foundation, a non-profit organization based in Berkeley, California, that has gathered a team of experts to manufacture and test Vasalgel.

Despite the excitement around the study, it could be awhile before Vasalgel hits the market; the product will require additional studies and approval by the U.S. Food and Drug Administration — a process that can take years.

Correction: A previous version of this story misstated that Vasalgel polymer is flushed out with saline, but it is actually dissolved with sodium bicarbonate solution.