The Food and Drug Administration approved a drug to treat Peyronie’s disease for the first time Friday. The condition can cause the male organ to curve dramatically when erect.

Doctors aren’t quite sure what causes Peyronie’s disease, though trauma during vigorous sex is one possible explanation. The curvature results from scar tissue inside the penis, which Xiaflex breaks down. A course of treatment consists of eight injections and four “penile modeling procedure[s].”

Somewhere between 5 and 10 percent of men have Peyronie’s disease, although for most of them, the curvature is hardly noticeable.

For others, the condition is more severe. “We joke around about it, but to someone who is in a relationship or attempting to be in a relationship who can’t perform sexually, this is a completely life-altering problem,” said Ryan Berglund, a Cleveland Clinic urologist. “You think about it all the time,” he said.

Xiaflex will give patients and doctors an alternative to surgery, which is the typical treatment for Peyronie’s disease. Surgery can cause erectile dysfunction and can shorten the penis.

Yet Xiaflex can also cause serious injury, and because of the risks, the FDA will only allow specially trained physicians and certified hospitals to administer it.

Shares of the drug’s manufacturer, Auxilium Pharmaceuticals of Chesterbrook, Pa., rose about 12 percent following the approval.

The FDA originally approved Xiaflex in 2010 to treat Dupuytren’s contracture, a disease that prevents patients from fully extending their fingers. The drug is an enzyme derived from a bacterium.