Eli Lilly and Co. wants to see its erectile dysfunction drug Cialis become the first of its kind to be sold to men without a prescription.

The plan involves a licensing deal between Lilly and French drugmaker Sanofi for over-the-counter sales in the United States, Europe, Canada and Australia. The move needs approval from regulators, who would weigh the risks of allowing the drug to be sold without a doctor’s appointment.

The two companies hope for a 2018 launch of what they’re calling Cialis OTC. That’s the same year patents for Cialis are expected to expire in the United States and Europe, allowing cheaper generics to take over and effectively dry up Lilly’s considerable profits from the drug. It generated $2.16 billion in sales last year and was Lilly’s fourth-best-selling drug.

The plan to sell Cialis over the counter would allow the Indianapolis drug maker to continue to profit from the drug as an impotence treatment.

Lilly didn’t reveal financial details of the deal with Sanofi. Under the pact, Sanofi will be responsible for commercializing nonprescription Cialis wherever it receives approval, and Lilly will make Cialis for Sanofi. The drug, sold in tablet form, is made by Lilly in Puerto Rico.

Cialis has been prescribed to more than 45 million men since its launch in Europe in 2002 and the U.S. a year later. The drug has been widely used and proved to be safe and effective, so it’s a good candidate to sell over the counter, said Dave Ricks, a senior vice president at Lilly.

In addition, over-the-counter sales would be a safer option for men than buying illicit forms of Cialis online without a prescription, Ricks said. He said many of the Cialis tablets advertised online are fake or adulterated.

Ricks said a large unmet demand exists for over-the-counter Cialis because many men suffering from impotence don’t feel comfortable talking to a doctor about the problem.

“Half of (American) men over 40 suffer ED,” Ricks said. “But the current market (for prescription ED drugs) only represents a fraction (of potential patients).”

The first prescription ED drug to market was Pfizer’s Viagra, introduced in the late 1990s. Pfizer applied in Europe several years ago to sell Viagra over the counter but later withdrew its request.

Lilly said Sanofi will take the lead in pursuing regulatory approval. One concern for regulators will be that Cialis isn’t supposed to be taken with medicines called nitrates that are often prescribed for chest pain. The combination can cause a dangerous drop in blood pressure.

Regulators also might be concerned that impotence is sometimes a sign of other medical problems, which won’t be discovered if men can buy Cialis without a checkup.

Ricks said it’s possible that regulators would approve OTC sales of Cialis only at certain doses and for some indications.