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Male Contraceptive Gel Proves 100% Successful In Monkey Trials


Katy Evans

Katy is Managing Editor at IFLScience where she oversees editorial content from News articles to Features, and even occasionally writes some.

Managing Editor


3D representation of Vasalgel blocking sperm in a human vas deferens. Parsemus Foundation 

A gel that can act as an alternative to the reversible vasectomy has been trialed in monkeys and found to be 100 percent successful as a long-term and reliable male contraceptive.

The product, Vasalgel™, has been previously trialed in rabbits and now with the success of the trial on rhesus monkeys, researchers hope that in the future it could be a potential alternative option to vasectomy for human males. The study is published in the open access journal Basic and Clinical Andrology.


Vasalgel™ is a non-toxic and non-hormonal gel that is injected into the vas deferens, the tubes that carry sperm from the testes to the penis. The gel fills the internal cavities of the tubes and acts as a barrier to the sperm. Previous tests in rabbits have shown that the procedure is easily reversible via an injection, too. 


Parsemus Foundation

"Vasalgel™ shows real promise as an alternative to vasectomy because research in rabbits has previously shown the product to be reversible,” lead author Catherine VandeVoort, from the California National Primate Research Centre, said in a statement. “Although it is possible to reverse a vasectomy, it is a technically challenging procedure and patients often have very low rates of fertility following reversal."

The researchers selected 16 rhesus monkeys for the surgery, 10 of which had already sired offspring. They were then monitored closely to ensure a healthy recovery before being placed back into their housing groups, which included adult fertile females. They were monitored for a breeding season (around six months) and the authors found that no pregnancies occurred during that time. The expected pregnancy rate for sexually mature females in similar normal conditions is about 80 percent.


Currently, there are two options for male contraceptives: condoms and vasectomies. There are, however, many different approaches being trialled, including an implant that can turn sperm off like a switch and an injection that slows sperms’ mobility with a 96 percent effectiveness. Unfortunately, there isn’t a huge amount of funding or a sense of urgency going into developing male contraceptives, as the side effects such as depression, acne, and hormone imbalances are considered too high – despite these all being accepted side effects of current female hormone-based contraceptions readily available and even prescribed by doctors.

Vasalgel™, however, does not affect sperm production or hormone levels, so side effects should not be an issue. Also, unlike vasectomies, where the tubes are cut and tied, making it harder (though not impossible) to reverse, the gel should be easily reversible via an injection of sodium bicarbonate, though this has only been tested in rabbits, not monkeys.   

The Parsemus Foundation, a non-profit organization that funded the work, said it plans to start a human trial as soon as funding is secured.


healthHealth and Medicine
  • tag
  • fertility,

  • sperm,

  • contraceptive,

  • male contraceptive,

  • Vasalgel™,

  • vasectomy,

  • reversible