In a surprising, and seemingly counterintuitive application of a wildly popular wrinkle relaxer, two Canadian urologists are testing Botox for impotence.

If it does for men what it has so far done in aged male rats, Botox may offer a persistent, long-acting (months at a time) way to restore erectile function in men, they believe.

Their preliminary data suggests Botox, or botulinum toxin injections, can increase blood flow to the penis by paralyzing the nerves that cause smooth muscles within the penis to contract.

Erections depend mainly on a good blood flow.

“The advantage of this would be that you inject it once, it lasts for six months potentially, and the pump would be primed every time you wanted to have sex,” said Dr. Sidney Radomski, a professor of surgery and urology at the University of Toronto.

Other forms of penile injection therapy have existed for years, but men have to self-inject every time they want to have sex. Meanwhile, Viagra and other pills that belong to a class known as PDE-5 inhibitors — drugs that act on the chemical signals that open up the blood vessels in the penis — have to be taken before sex, or daily. They can also cause side effects such as headache and heartburn. As well, Viagra doesn’t work for a third or more of men who try it, said Dr. Gerald Brock, professor of surgery at Western University in London.