A male contraceptive gel has been successfully tested in monkeys, bringing the prospect of an alternative form of birth control for humans one step closer.

Vasalgel is injected into the two vas deferens tubes that carry sperm out of the testicles, and creates a blockage.

It has also been designed to provide a reversible alternative to vasectomy.

A study in rabbits last year showed the contraceptive gel, which is not classified as a pharmaceutical product, can be removed by flushing the duct with baking soda solution.

In the new trial, the gel, made by the non-profit Parsemus Foundation in Berkeley, California, prevented any conceptions occurring in a test group of 16 rhesus monkeys.


Clinical trials on humans are expected to begin next year.

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Lead scientist Dr Catherine VandeVoort, from the California National Primate Research Centre, said: "Vasalgel shows real promise as an alternative to vasectomy.

"Importantly, we show that the method of Vasalgel placement is safe and produced fewer complications than usually occur with a vasectomy.

"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."

One of the treated monkeys showed signs of sperm granuloma, a hard build-up of sperm in the vas deferens - a non-serious complication that affects around 60% of men undergoing a vasectomy, researchers said..

Professor Adam Balen, chairman of the British Fertility Society, said: "If free of side effects then this novel approach has the potential for great promise as a male contraceptive.

"It is essential to know that the reversibility remains, irrespective of the duration of use."

Allan Pacey, professor of andrology at the University of Sheffield, said the idea of trying to replace the traditional method of vasectomy with a gel is not a new one, but added: "We haven't seen much progress in developing the idea in recent years, so this study is a useful step in the right direction."