A new male contraceptive gel tested in rhesus monkeys could prove to be a reversible alternative to vasectomy
By Kennedy Lamb
A new contraceptive gel is highly effective in preventing pregnancy in female partners of treated males, according to a study published in early February 2017 in the journal of Basic and Clinical Andrology.
The study was carried out on rhesus monkeys, which have a similar reproductive structure to humans. None of the partners of the treated males became pregnant.
The gel adheres to the tissues of the vas deferens – the duct which transports sperm from the testicles to the urethra – and formed a barrier, preventing the passage of sperm.
In a trial conducted in 2016 on rabbits, an injection of sodium bicarbonate (baking soda) into the vas deferens successfully flushed the gel from the reproductive system, allowing for the return of normal sperm flow.
“Vasalgel shows real promise as a reversible alternative to a vasectomy,” says Catherine VandeVoort, the head of the California National Primate Center, who directed the study.
VandeVoort says that the insertion of the gel produces fewer complications than usually occur with a vasectomy.
A vasectomy – the surgical cutting and sealing of the vas deferens is reversible, but the procedure is difficult and fertility remains low in men who undergo reversal. Other than condoms, which have a 2% fail rate, vasectomy is currently the only contraceptive option for men.
The study was carried out in an environment that mimics human sexual behavior. 25 monkeys lived in outdoor pens and mated freely for a period ranging from one to two years.
Each enclosure included one to three sexually mature males and two to nine mature females. The monkeys lived together for at least one breeding season; seven of the males lived among the same group of females for two years. All females in the study had previously given birth to offspring, proving their fertility.
Researchers say that in a similar housing situation, they would expect 80% of females to conceive in a breeding season without the use of contraceptives. But with all of the males treated with the contraceptive gel, none of the females became pregnant.
Out of the sixteen male monkeys treated with the gel, only one experienced a complication: sperm granuloma – a hard build-up of sperm in the vas deferens. Sperm granuloma occurs in 60% of traditional vasectomies in humans. There were significantly fewer cases of sperm granuloma in monkeys treated with the contraceptive gel than typically found in vasectomy cases, according to researchers.
Research is currently being conducted to test the long-lasting effects of the gel. They plan to continue testing the reversibility of the contraceptive before testing the gel on humans.