RISUG: Birth Control for Men

According to an enthusiastic article on the Internet, “The Best Birth Control In the World Is For Men.”

It’s called RISUG: Reversible Inhibition of Sperm Under Guidance. It involves a minor surgical procedure in which the vas deferens is exposed and pulled outside the scrotum by the same techniques used for a vasectomy. A copolymer, powdered styrene maleic anhydride (SMA, for which the method was previously named) combined with dimethyl sulfoxide (DMSO) is then injected into the vas deferens. The polymer coats the walls of the vas and kills the sperm as they swim by. The mechanism is not understood, but the developer thinks the polymer’s mosaic of positive and negative charges causes the membranes of the sperm to burst, rendering them immotile.

RISUG is rapidly effective: in a phase II clinical trial in India, viable sperm were absent as soon as 5 days after the procedure. They say there have been no pregnancies in the first months “other than a handful of cases in which the RISUG was not injected properly.” (One wonders how they determined that it was not injected properly: by the fact that pregnancy occurred? Could this be just a rationale to explain away failures? Or to spare patients the embarrassment of discovering the wife had another sperm donor?) The contraceptive effect is said to last for a decade or more; it might require repeat injections every 10 years.

In contrast to vasectomy, RISUG can be reversed by injecting DMSO or bicarbonate and using a combination of vibration, a low electric current, and rectal massage to dislodge the polymer and move it through the vas deferens.

It is not yet approved in India, but it has already been patented in several countries. Efforts are underway to seek FDA approval in the US under the name Vasalgel, but don’t look for it on the market anytime soon: preliminary studies on rabbits are just getting started. 

It sounds crazy, but there is evidence to support it. A search for RISUG on PubMed brings up 18 articles. Some are lab studies, some are not directly relevant, and some are reviews of contraceptive methods; but there are a couple of very encouraging studies in monkeys and a report of a phase II human trial with 12 subjects. 

An article in Wired calls it the revolutionary new birth control method for men and includes a video so you can watch the actual procedure. It says:

It’s the brainchild of a maverick Indian scientist named Sujoy Guha, who has spent more than 30 years refining the idea while battling bureaucrats in his own country and skeptics worldwide. He has prevailed because, in study after study, RISUG has been proven to work 100 percent of the time. Among the hundreds of men who have been successfully injected with the compound so far in clinical trials, there has not been a single failure or serious adverse reaction. The procedure is now in late Phase III clinical trials in India, which means approval in that country could come in as little as two years.

There are some worrisome red flags here: lone genius, battling the establishment, reference to “study after study” when Phase III trial results are still pending, and the claim that it is 100 percent effective. No contraceptive measure is 100 percent effective, not even hysterectomy: abdominal pregnancy can occur even after a total abdominal hysterectomy.


RISUG may be a promising means of birth control for males, but it’s too early to draw any conclusions. The current media hype is unwarranted. Science will have to run its course and complete well-designed clinical trials before the method can be recommended.

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