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When people think impotence, they think Viagra. Soon, that may change.
Two “sons of Viagra” are close to reaching the market, and doctors say these new drugs may have some definitive advantages. They work in a similar way, but they seem to act faster and cause fewer of the trademark Viagra side effects: headaches, nasal congestion, flushed faces and blue vision.
To tout the new drugs’ advantages, their makers can unleash some serious marketing firepower — sufficient to give Pfizer Inc., which effectively created the pharmaceutical market for alleviating erectile dysfunction when it launched Viagra a few years ago — a run for its money. A lot of money is at stake. Viagra’s sales totaled $1.3 billion last year and are projected to rise to $1.6 billion this year.
Cialis and vardenafil act in the same way as Viagra, by blocking an enzyme called phosphodiesterase-5, or PDE-5, and in the process relaxing smooth muscle cells in the penis and elsewhere. In causing these muscles to relax, the drugs effectively increase blood flow to the penis.
Though they work in similar ways, Cialis, vardenafil and Viagra are distinctly different chemical entities. Some urologists say vardenafil and Cialis are more effective at blocking the PDE-5 enzyme and hence potentially more potent than Viagra. This means they could act as well as, or better than, Viagra at smaller doses. They also interact with fewer other molecules and hence might have fewer side effects.
In the looming marketing battle, Viagra starts out with some advantages, Pfizer argues. The company has conducted more than 80 studies of Viagra, says Michael Widlitz, a vice president at Pfizer, and “no competitor can hope to ascend this mountain of efficacy and safety data.”
Drug-industry executives estimate that 30 million European men suffer from
No one can make a definitive comparison between the drugs because there have been no public head-to-head clinical trials. But the newcomers are already zeroing in on what they believe are their drugs’ advantages over Viagra. Cialis, for instance, gave men improved ability to have sex for up to 36 hours, according to results from a study presented at a medical conference recently. In contrast, Pfizer recommends that men have sex within four hours of taking Viagra.
“Patients should not have to worry about watching the clock and planning their sex life around the time they take a drug,” says Paul Clark, chief executive officer of Icos. “Cialis allows you to have a more spontaneous relationship.”