This 2003 article, Long-term Tolerance With Viagra suggests that there is a consensus amongst authorities that sildenafil (Viagra) does not have a tachyphylactic effect - i.e. it doesn't diminish in its effectiveness after repeated use:
The results of the El-Galley study were largely discounted upon poor follow-up; 50% of the men on sildenafil did not respond to a telephone interview at 2 years' follow-up. In contrast, a 3-year follow-up study in nerve-sparing radical prostatectomy patients (n = 41) revealed that 71% (29/41) were still responding to the same dose of sildenafil.[4] Of the 29% of dropouts, half (6/12) stopped because of return of spontaneous erections, with only 5 of 12 gradually losing efficacy. Hence, most authorities have attributed loss of sildenafil efficacy not to tachyphylaxis, but to progression in organic disease from associated comorbidities and aging.
However, a recent study using cultured rat cavernosal smooth muscle cells demonstrated molecular upregulation of the phosphodiesterase type 5 (PDE-5) enzyme when the cells treated with high doses of sildenafil for at least 7 days.[5] These findings suggest that sildenafil is safe and effective when used at normal clinical doses and recommended dosing frequencies. However, additional clinical research will be needed to evaluate the tachyphylaxis effect in chronic PDE-5 inhibitor use, especially when these agents possess long half-lives.
Is the article conclusive? Are there any other studies that backup this claims? Twelve years have passed - is this still the consensus of medical world now?
