Can you develop a tolerance to Viagra? The large long-term studies say no: most men who kept taking sildenafil for one to four years kept the same benefit. The European label states that "The safety and efficacy of sildenafil was maintained in long-term studies" (EMA product information). One small survey did find some men needing a higher dose over time. When Viagra seems to stop working, the usual reasons are the condition behind the erection problem, a new medicine, or the way it is being taken.
What do the long-term studies show?
That the effect holds. In 1,008 men with erectile dysfunction who took sildenafil for 36 or 52 weeks at doses of 25 to 100 mg, 92% and 89% said it had improved their erections, and the authors concluded that "Long-term therapy does not diminish the efficacy of sildenafil" (Steers et al., 2001). In a four-year study of 979 men, more than 94% said at every yearly check that they were satisfied with its effect on their erections, and 6.3% stopped because it did not work well enough. The authors read this as evidence against tachyphylaxis, the medical term for a medicine losing its effect with repeated use (McMurray et al., 2007). Both were open-label extensions: the men had already been through earlier trials, and there was no placebo group.
Is there any evidence that it wears off?
One survey suggests it might for some men. A US clinic phoned its patients during their first year on sildenafil and again two years later. Of those followed for two years, 20% had needed a higher dose for the same effect and 17% had stopped because it no longer worked; the authors called this "a possible tachyphylaxis effect". They found no link between needing a higher dose and how often the tablets were taken (El-Galley et al., 2001). It was a telephone survey with no comparison group, many men could not be reached, and they had different causes of erectile dysfunction, including prostate removal and diabetic or arterial disease, so a change in the condition itself cannot be ruled out.
Why might Viagra seem to work less well over time?
Usually because something else has changed. Its effectiveness can decrease over time if underlying health conditions worsen: how well sildenafil works depends on the cause, with better erections reported by 84% of men whose erectile dysfunction was psychological, 59% of diabetic men and 43% after removal of the prostate (EMA product information). High blood pressure, high cholesterol, heart disease and obesity all contribute to erection problems, and some medicines for blood pressure, cholesterol, depression or prostate cancer can cause them; so can alcohol, smoking, stress and relationship problems (healthdirect — Erectile dysfunction). How the tablet is taken matters too: a heavy meal slows it, and it works only with arousal (Viagra CMI); see how to increase the effects of Viagra.
Does taking it often make it stop working?
The evidence says no. In the survey above, needing a higher dose was not linked to how often men took it (El-Galley et al., 2001). What stopping does is clear: after 16 weeks on sildenafil, men switched at random and without knowing to a placebo saw the gains in how often and how long they had erections return to pre-treatment levels, while those who stayed on it kept them (Christiansen et al., 2000). Viagra treats erection problems while you take it; it does not cure them. Whether it is habit-forming is answered in can you become dependent on Viagra?
What should you do if Viagra stops working as well?
Tell your doctor rather than taking more. The leaflet says that if it does not help you get an erection that lasts long enough, "tell your doctor. In these cases, your doctor may decide that you need a higher dose" (Viagra CMI); one tablet a day is the limit, as explained in can you take multiple Viagra pills safely? A change is also worth checking for its own sake: erection problems are often the first sign of heart disease or high blood pressure (healthdirect — Erectile dysfunction). If tablets no longer help, the options include alprostadil injections or a vacuum device (Healthy Male). More in causes and solutions for Viagra not working.
The short answer
Most men do not develop a tolerance to Viagra: in studies of one to four years, it kept working for about nine in ten. One small survey found some men needing a higher dose over time; it could not tell whether the medicine or their condition had changed. If it works less well than it did, see your doctor, who can look for the cause and adjust the dose. More in our guide to why Viagra may not work.
