Viagra and erections: Do the benefits persist?
When Viagra (sildenafil) burst on the scene in 1998, it was a revolutionary development. Within months, it became clear that the drug could help about 70% of men with erectile dysfunction. Within a year, the medication had established an enviable safety record, even for men with stable heart disease (though it should never be used by men taking nitrates in any form or by men with unstable cardiovascular problems).
These early observations have held up, but as Viagra has settled into the mainstream, doctors are starting to ask how it affects men who have used it for several years.
Viagra is not a long-term cure, but a temporary corrective for men who have difficulty in attaining or maintaining erections satisfactory for intercourse. A man should take the pill about an hour before he expects to have sex. By itself, the medication does not produce an erection, but it will kick in when erotic stimulation occurs. However, Viagra’s effects wane, and after about four hours its benefits are nearly gone. Still, despite this brief window of opportunity, men should not take the drug more than once in a 24-hour period.
Viagra is short-acting, but doctors hoped it might have long-lasting benefits. That’s because when the penis is flaccid, its tissues get relatively little oxygen. An erection brings oxygen-rich blood to the organ, which may help keep the tissues healthy. Even without sexual stimulation, the average man develops three to five erections during sleep every night, each lasting up to 30 minutes. Men whose erectile dysfunction has a psychological cause retain nocturnal erections, but men with physical causes of impotence do not.
Doctors hoped that by bringing extra blood to the penis, Viagra might actually improve erectile function in men who used it regularly over time. These hopes were bolstered by two small studies that found a bedtime dose of Viagra could improve spontaneous nighttime erections in men with both psychological and organic impotence. But as experience has accumulated, it has become clear that Viagra will not put itself out of business. Despite the theoretical long-term benefits of erections, men who need Viagra continue to need it despite frequent long-term use.
If long-term use doesn’t decrease a man’s need for the drug, can it have the opposite effect? Can the body get used to Viagra so that higher doses are needed just to preserve its function? Doctors call it tachyphylaxis, a well-known effect that explains why people who overuse certain painkillers or sleeping pills need escalating doses to relieve pain or get to sleep.
Viagra comes in three doses, 25, 50, and 100 mg. Most men start with 50 mg and adjust the dose up to 100 mg or down to 25 mg, aiming for the lowest dose that works well. If Viagra were to lose its punch over time, though, men might find themselves needing higher doses to maintain benefit. In fact, a study of 200 men who had used Viagra for at least two years found 20% had to increase their dose to continue getting good results, and another 17% stopped using the drug because its benefits were lost, even with a 100 mg dose. But this loss of benefit could result either from the body’s getting used to the medication or from a gradual worsening of the disorder that caused impotence in the first place. However, another new study reported that Viagra’s side effects also diminish over time, suggesting that some men do adapt to the medication, thus diminishing its activity.
The bad news is that most men who need Viagra continue to need it over time. The good news is that 83% of men will continue to respond, though a quarter of them may need higher doses after several years. More research is needed to see how Viagra affects men after even longer periods of use. It’s a good example of why every new medication should be reevaluated as experience mounts — and a reminder that time stands still for no man.