Health regulators on Friday approved Vivus Inc.‘s avanafil treatment for erectile dysfunction, giving the small company, which has struggled to bring a weight loss drug to market, a potentially lucrative commercial product.

The U.S. Food and Drug Administration said the pill, which will compete with Pfizer’s Inc’s Viagra and other ED drugs, will be sold under the brand name Stendra.

Stendra, which belongs to the same class of medicines called PDE5 inhibitors as Viagra, Eli Lilly’s Cialis and Levitra, sold by GlaxoSmithKline and Bayer, works by increasing blood flow to the penis.

The drug is awaiting a European approval decision.

Doctors should prescribe the lowest dose of Stendra that provides benefit, the FDA said. It has been approved at doses of 50 milligrams, 100 mg and 200 mg.

“This approval expands the available treatment options to men experiencing erectile dysfunction, and enables patients, in consultation with their doctor, to choose the most appropriate treatment for their needs,” Victoria Kusiak, deputy director of the Office of Drug Evaluation in the FDA’s Center for Drug Evaluation and Research, said in a statement.

Patients are instructed to take Stendra 30 minutes before sexual activity but in clinical trials it has been shown to work in as little as 15 minutes.

The most common side effects reported in greater than 2 percent of patients in the clinical studies included headache, flushing of the face and other areas, nasal congestion, common cold-like symptoms and back pain.

The drug carries the same cautions as its rivals, including that it should not be used by men who also take nitrates due to the potential for a sudden dangerous drop in blood pressure and the warning to see a doctor if an erection lasts more than four hours.

Vivus shares were up 4.5 percent at $25.53 on Nasdaq before being halted prior to the FDA announcement.

###

(Reuters)