Just months after the trial of a hormonal birth control injection for men was halted when some complained of side effects, there is new hope of a way to block sperm — and thus pregnancy — without a condom.

Researchers have reported that a gel injection completely prevented pregnancy among monkeys, opening the door for human trials. The Parsemus Foundation said in a statement about the work that the results confirm findings of previous tests on rabbits, that the Vasalgel blocks the passage of sperm from the testicles into the penis when injected into their connecting tube called the vas deferens.

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The related study in Basic and Clinical Andrology describes the way the contraceptive works as filling up the passageway to the penis. It “acts as a mechanical barrier to the passage of sperm.” And if the male using the birth control method reverses direction and wants to have children, the gel could be flushed out.

The Vasalgel “could be the first long-acting, non-hormonal, potentially reversible male contraceptive to reach market,” according to the foundation.

For the men who experienced side effects while taking hormonal birth control, the study says with the Vasalgel the side effects were comparable to what men may experience after a vasectomy. “The presence of Vasalgel appears to be well-tolerated and placement resulted in minimal complications.”

The monkey trials were proof that the gel could work on large animals that are “anatomically similar to humans,” the Parsemus Foundation said, and now the researchers are preparing for human trials. If they are successful, men could have a method of birth control other than condoms, vasectomies, and “pulling out.”

“The demand for new male contraceptive methods is growing,” the organization said. “Surveys indicate that the majority of men would be interested in using a new contraceptive, and about 20 percent of couples already rely on existing male methods for reproductive control.”

Source: VandeVoort CA, Colagross-Schouten A, Lemoy M, Keesler RI and Lissner E. The contraceptive efficacy of intravas injection of Vasalgel™ for adult male rhesus monkeys. Basic and Clinical Andrology. 2017.

See also:

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Why Men Don’t Know About Their Sexual Health