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As Mesher's story suggests, and many doctors insist, more isn't necessarily more with Viagra. Known to chemists by the less evocative name of sildenafil (the word Viagra, redolent of both "vigor" and "Niagara," had been kicking around Pfizer for years, a brand name in search of a product), the drug began life as a heart medication designed to treat angina by increasing blood flow to the heart. Sildenafil, it turned out, wasn't so good at opening coronary arteries, but happy test subjects did notice increased blood flow to their penises, a side effect brought to Pfizer's attention when the test subjects were reluctant to return their leftover pills. The medication works by suppressing the effect of the naturally occurring enzyme phosphodiesterase type 5 (PDE5), which causes an erection to subside after orgasm by breaking down the body chemical known as cyclic GMP. It is cyclic GMP that initiates the muscular and vascular changes that lead to an erection in the first place. While PDE5 is always present in the penis, cyclic GMP is produced only during arousal. The catch in impotent men is that they may not produce enough cyclic GMP to temporarily "win out" over the PDE5. Thus the efficacy of Viagra: by strong-arming PDE5, it allows a little bit of one's cyclic GMP to go a long way.
One more nugget of possibly boring but crucial biochemistry: the erectile tissue in the penis has a finite number of receptors for cyclic GMP. This means that a normally functioning man with adequate levels of the chemical shouldn't get any more bang for his buck by gobbling Viagra; the variations anyone feels in his or her sexual response are due to factors outside the drug's purview. At the same time, Pfizer hasn't done any testing of the drug on nonimpotent men to prove the point, but it's hard to imagine that biochemical nitpicking is going to stop people from experimenting. Certainly it will be hard for wet blankets and smarty-pants to compete with the siren calls coming out of sex clinics around the country from men "feeling 18 again."
"If you can have an erection naturally, you probably won't need Viagra," says Thomas Burnakis, pharmacy clinical coordinator at Baptist Medical Center in Jacksonville, Fla. "It's not going to make your erection harder or last longer. But I can guarantee you that if you walk in and say, 'Doc, I'm having trouble keeping my flag up,' most physicians are not going to insist on testing. What's to keep you from using it? Absolutely nothing. And just as with fen/phen, while a lot of doctors said they would not give that drug, a lot of clinics were prescribing it. It's going to be a moneymaking procedure. They'll give a cursory exam, charge you for that and write the prescription"--a prediction that has already been borne out on the Internet. According to Pfizer, there's no evidence that overeager users could develop a physical addiction to Viagra. But as for a psychological addiction, that is uncharted territory.