If approved for over-the-counter use, Cialis could gain an advantage over prescription competitors like Viagra, sold by Pfizer. But it is not clear whether the Food and Drug Administration or other regulatory bodies overseas would approve such a move: In 2008, Pfizer abandoned an effort to make Viagra available without a prescription after the European Medicines Agency raised concerns.
"Millions of men worldwide trust Cialis to treat E.D.," or erectile dysfunction, said David A. Ricks, president of Lilly Bio-Medicines, the unit of Lilly that oversees Cialis. "We are pleased to work with Sanofi to pursue a path that could allow more men who suffer from E.D. to obtain convenient access to a safe and reliable product without a prescription."
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Although more than 45 million men have taken Cialis, according to Lilly, the drug is not without risks: Like similar treatments, it should not be taken with some heart medications because it could cause an unsafe drop in blood pressure.
A spokeswoman for the F.D.A. said the agency would need to review what types of studies would be needed for an erectile dysfunction drug like Cialis to be sold without a prescription.
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Drug companies frequently seek approval to move popular drugs to over-the-counter sales in an effort to hang onto sales when a best-selling product loses its patent protection. In 2003, AstraZeneca got approval to sell its blockbuster heartburn drug Prilosec without a prescription, and in 2012, it sold over-the-counter rights to a similar drug, Nexium, to Pfizer. The nonprescription product, Nexium 24HR, went on sale this week.
Sales of erectile dysfunction drugs have soared since Viagra was approved in 1998, but the companies that sell them have also struggled against the social stigma of male impotence. Many men, unwilling to visit a doctor for a prescription — or seeking lower prices — have turned to online marketplaces, many of which sell the drugs illegally. Last year, in an effort to recoup some of those lost sales, Pfizer began selling Viagra to consumers through its own website.
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The move to make Cialis available without a prescription could be seen in a similar vein, as removing one of the hurdles — a visit to the doctor — to getting treatment.
But one urologist, Dr. Kevin L. Billups of the Johns Hopkins School of Medicine, expressed concern about moving Cialis to an over-the-counter product because, he said, erectile dysfunction can be an early warning sign for more serious conditions like diabetes and heart disease.
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"Maybe you're missing an opportunity to pick up something else," said Dr. Billups, who is director of the school's Men's Health and Vitality Program.
Cialis, which was approved in the United States in 2003, brought in $2.2 billion in worldwide sales last year. Viagra, which recently lost its patent protection in several countries, brought in $1.9 billion.
—By Katie Thomas, The New York Times