Sanofi sees an attractive opportunity in the rampant market for counterfeit Viagra: luring men away from dodgy online pharmacies with an over-the-counter version of a competing erection drug.

The French drugmaker plans safety and efficacy studies to support an application to produce a non-prescription version of Eli Lilly & Co.'s Cialis. One selling point is to provide a legal and effective alternative to fake copies of Pfizer's Viagra and other drugs, said Vincent Warnery, senior vice president of global consumer health care at Sanofi.

"The vast majority of men don't consult their doctor on erectile dysfunction," Warnery said at a consumer health-care conference in London Wednesday. "Men search online for drugs they can access directly, and in doing so they expose themselves to the huge risks of counterfeit drugs."

Fake versions of Viagra, one of the most copied medicines in the world, are abundant on the Internet, and that puts consumers at risk. Of more than 10,000 online outlets surveyed last year by the National Association of Boards of Pharmacy, 97 percent were out of compliance with U.S. pharmacy laws and standards.

Sanofi, based in Paris, said last week it agreed to work with Lilly on over-the-counter Cialis, a $2 billion a year drug that loses patent protection in 2017. Lilly turned to Sanofi because the Indianapolis-based company doesn't have as much experience with non-prescription medicines, Warnery said.

"Looking at what Lilly has shown us, we believe we are in a good place," the executive said.

Even so, the approach to regulators follows a similar attempt by Pfizer that the New York-based company abandoned. Pfizer sought approval for an OTC version of Viagra in Europe and withdrew its application in 2008 given concerns raised by the European Union's drug regulator.

Guido Rasi, executive director of the European Medicines Agency, said the regulator would need to "seriously analyze" why Pfizer's over-the-counter application wasn't successful.

Pfizer's little blue pills caused a sexual revolution for millions of men when they were introduced 16 years ago, replacing treatments that included penile injections and surgery. More than 18 million Americans older than age 20 suffer from erection difficulties, according to Johns Hopkins University's Bloomberg School of Public Health.

Interpol said last month it shut down more than 10,000 websites offering illicit pharmaceuticals. Among the 9.4 million medicines seized were erectile dysfunction pills, according to the police agency.

Given Sanofi and Eli Lilly's plan, Pfizer may revisit making non-prescription Viagra, said Andy Tisman, consumer health-care consultant at IMS Health in London.

Pfizer reached an agreement in December with Teva Pharmaceutical Industries Ltd. that permits the Israeli drugmaker to market a generic version of Viagra in the U.S. starting in 2017.

"We are evaluating a number of prescription drugs for potential switch to non-prescription status, and are focusing on categories that will have the greatest positive impact to people and the health-care system overall," Sally Beatty, a Pfizer spokeswoman, said in an e-mail.