A Vivus Inc. pill that is supposed to provide erections within 15 minutes, about half the time or less than Eli Lilly and Co.'s Cialis or Pfizer Inc.’s Viagra,  has received U.S. regulatory approval.

The Food and Drug Administration on Friday cleared the erectile dysfunction treatment, called Stendra, the agency said in a statement. Erectile dysfunction is the inability to get or keep an erection firm enough for sexual intercourse.

The drug, known chemically as avanafil, is the sole product on the market for Mountain View, Calif.-based Vivus, which is seeking a partner to sell the medicine in the United States.

New York- based Pfizer’s Viagra, the top-selling erectile dysfunction pill with $2 billion in sales last year, works in 30 minutes to an hour, according to the drug’s website.

Cialis, which works in 30 minutes or less, had worldwide sales of $1.88 billion in 2011, accounting for 8 percent of Indianapolis-based Lilly's revenue.

“I do think it’s a differentiated product,” Michael King, an analyst with Rodman & Renshaw LLC in New York, said about Stendra. Unlike competitors, Vivus’s drug features “rapid onset; rapid off.”

Avanafil may have $68 million in sales next year, according to the average estimate of six analysts compiled by Bloomberg. Revenue may peak at $459 million in 2017, King said.

Sales may be slowed at first by Vivus’s capacity to market the drug. The company is discussing deals with potential partners to sell the medicine, Vivus said.

The erectile dysfunction drug also will soon face generic competition. Patents for Cialis and Levitra expire in 2016 and 2018, respectively. Cialis is likely to see generic competition in 2017, and in generic Viagra is expected to be available in 2019, King said.

Vivus “will be rolling a rock up a hill on the generic side,” King said in a telephone interview.

The National Institutes of Health estimates that erectile dysfunction affects as many as 30 million men in the U.S.

“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 III in the FDA’s Center for Drug Evaluation and Research, said in the prepared statement.

Stendra in some rare cases may cause color vision changes and sudden loss of vision in one or both eyes, according to the FDA. The most common side effects are headache, redness of the face, nasal congestion, cold-like symptoms and back pain. The drug also shouldn’t be used by men who take nitrates, which are used to treat chest pain, because the combination may cause a sudden drop in blood pressure, the agency said.

The pill’s side effects are similar to other erectile dysfunction drugs on the market, Barbara Troupin, vice president of medical affairs for Vivus, said last month at a conference.

Vivus made the Muse penile suppository before selling the rights in November 2010 to Meda AB, a specialty pharmaceutical company in Solna, Sweden, for about $23.5 million.

In addition to avanafil, Vivus is awaiting a July 17 FDA decision on Qnexa, which potentially would be the first obesity pill approved in 13 years.

Vivus is competing with Arena Pharmaceuticals Inc. and Orexigen Therapeutics Inc. to bring the first weight-loss drug to market since Roche Holding AG’s Xenical in 1999. FDA advisers voted Feb. 22 in favor of Vivus’s Qnexa, while raising concerns that the drug may potentially contribute to heart risks and birth defects.

The company submitted earlier this month a risk evaluation and mitigation strategy in an effort to win approval for the obesity drug.