Pfizer Begins Selling Viagra Online Niko J. Kallianiotis for The New York Times Pfizer now sells Viagra, the erectile dysfunction drug that is one of its chief money makers, online to men with a prescription. Pfizer has taken the unusual step of selling its erectile dysfunction drug, Viagra, to consumers on its Web site, in an effort to establish a presence in the huge online market for the popular blue pill, considered to be one of the most counterfeited drugs in the world. Viagra is one of Pfizer's marquee drugs - the company said it brought in more than $2 billion in sales in 2012 - but some drug experts estimate Pfizer could be losing hundreds of millions of dollars a year to a prolific black market of online pharmacies that cater to men too embarrassed to buy the drug through traditional means. As of Monday, in an arrangement with CVS/pharmacy, patients in the United States with a valid prescription for Viagra are able to fill their order through the new Web site, where the sentence "Buy real Viagra" is featured prominently. Patients will still need to visit a doctor, but they will be spared the additional trip to the pharmacy counter. If Pfizer's move is successful, more drug makers could follow suit, especially for other products that treat conditions carrying social stigmas, such as weight loss. "This could be the prelude to a vast number of products" of medical importance being sold online, said Roger Bate, a resident scholar at the American Enterprise Institute and an expert in counterfeit drugs. But others cautioned against such predictions, saying that Viagra might be particularly well suited to online sales because of its powerful brand recognition and the widespread competition from counterfeiters. Victor Clavelli, a marketing executive at Pfizer whose portfolio includes Viagra, said the drug appeared in about 24 million Internet searches a year, often in phrases like "buy Viagra" - well in excess of the approximately eight million Viagra prescriptions written in the United States last year, according to the research firm IMS Health. "A lot of those patients get diverted into an illegal counterfeit market," Mr. Clavelli said. Our goal is to just make sure those patients actually get the real Viagra. Since Viagra arrived on the market in 1998, Pfizer has sought to minimize the stigma around male impotence - rebranded as erectile dysfunction, or E.D. - by enlisting celebrity endorsers like the former Republican presidential candidate Bob Dole and encouraging men to have the "Viagra talk" with their doctors. But even as men flooded doctors" offices for prescriptions for what is commonly known as "the little blue pill," others turned to a vigorous black market, whose growth mirrored an explosion in online commerce. "Viagra is one of the classics," said Mr. Bate. Diet pills for women and erectile dysfunction medicines for men are the most sought-after medicines online. Matthew J. Bassiur, vice president of Pfizer Global Security, said in a statement that the company had seen counterfeit medicines manufactured "in filthy and deplorable conditions, yet some people do not realize the risks that this poses to their health and safety, our top priority." He added that samples of counterfeit Viagra tested by Pfizer labs had contained "pesticides, wallboard, commercial paint and printer ink." "These findings," Mr. Bassiur said, "motivate us to continue our aggressive global efforts to stop those who prey on unsuspecting patients." Pfizer said it conducted a survey in 2011 in which it evaluated 22 Web sites appearing in the top search results for the phrase "buy Viagra." Chemical analyses found that about 80 percent of the pills were counterfeit. The fake Viagra pills contained only about 30 to 50 percent of the active ingredient, sildenafil citrate, compared with the actual product. Not all medicines purchased online are fake, however - many pharmacies, based both in the United States and abroad, require a doctor's prescription and sell valid versions of drugs. Importing drugs from other countries is technically illegal, although the federal government generally does not prosecute individuals who purchase medicines in small amounts for their own use. The problem, Mr. Bate said, is that it is difficult for consumers to distinguish the legitimate pharmacies from the illicit ones. "For the very nervous purchaser online," he said, Pfizer is "a name brand you know really well, and the chance of your buying a counterfeit is close to zero." He noted, however, that some cash-paying customers may balk at the purchase price. The average list price for Viagra is about $22 a pill, while many online pharmacies sell it for about $10. Some industry analysts saw Pfizer's move as part of a continuing effort to market drugs directly to consumers, bypassing insurance companies that can be reluctant to pay for so-called lifestyle drugs or that force consumers to pay hefty co-payments. The company said about 90 percent of privately insured patients in the United States receive coverage for Viagra, and co-payments can range from $29 to $49. Customers who buy Viagra through the Pfizer Web site get three free pills in their first prescription - which typically consists of six pills - and 30 percent off their second prescription. Mr. Clavelli, the Pfizer marketing executive, said the current Viagra discount was not unique to customers who buy through the online service and had been offered to patients online and at doctors" offices for months. Another drug maker, AstraZeneca, has a similar arrangement with an outside pharmacy to sell the breast-cancer treatment Arimidex to patients. Viagra has about 49 percent of the market for sexual dysfunction treatments, followed by Cialis, which holds 39.7 percent, and Levitra, with 8.6 percent, according to IMS Health.