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The Male Birth Control Shot Now Works in Monkeys

Guess whose scrotums are next?
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If you hadn't heard, there's a nonprofit working on a long-acting, hormone-free male birth control shot—and a study out today has confirmed its efficacy in monkeys. The treatment, called Vasalgel, consists of an injection into the vas deferens, the duct that transports sperm to the urethra where it mixes with seminal fluid. Getting a shot of Vasalgel in the nuts (with a local anesthetic) works like a vasectomy in that it blocks the passage of sperm, except unlike a vasectomy, this semi-permeable hydrogel plug can be dissolved with a second injection of sodium bicarbonate, aka baking soda.


The nonprofit Parsemus Foundation has funded research showing that Vasalgel blocked sperm in rabbits and was successfully reversed (article in press). But in the rabbit study, researchers just analyzed the animals' post-injection semen to make sure it didn't contain sperm. Today's study sought to show that Vasalgel could not just eliminate sperm in a lab test, but prevent pregnancy for real.

Researchers from the California National Primate Research Center injected 16 rhesus monkeys with the gel and, after a week of recovery, let them return to their co-ed group housing. (Yes, these lady monkeys had gotten pregnant at least once before.) They followed the monkeys for more than a year, seven of them for more than two years, and there were zero pregnancies. They reported their findings in the journal Basic and Clinical Andrology.

Now that they've established that the injection is effective and well-tolerated in animals, they're preparing for the first clinical trial in humans. They'd only recruit men who are planning to get a vasectomy anyway, and the trial would be to make sure that it works; after that, they'd conduct more studies to see if the injection is reversible in humans.

Some men might not want to have "their dick clogged with gel," as Broadly once described the process, but for others, a quick injection is more appealing than having to take a pill every day. Plus, Vasalgel is further along in the pipeline than male contraceptive pills. Parsemus Foundation's executive director Elaine Lissner told VICE News in April that they had 32,000 people on their mailing list. But, she added: "Until reversal is sure, it's not going to be for men who want children later unless they also freeze their sperm."

Update 4/5/17: The study that showed Vasalgel was successfully reversed in rabbits has been published in the journal Basic and Clinical Andrology.