Doubtfulness
Is there any indication that there is mental attitude or habituation when sildenafil is used over long periods of time?
Reaction from Thespian J.
G. Hellstrom, MD, FACS
Professor of Urology
Erectile dysfunction (ED) is defined as the unfitness to attain or maintain an adequate penile building for satisfactory sexual sexual congress. Since the making known into clinical noesis of viagra (sildenafil; Pfizer Pharmaceutical Corp.; New York, NY), there has been a dramatic action in the artistic style algorithm for men with ED.
No longer do all men wretchedness from ED have to repair to the surgical positioning of a penile prosthesis, intracavernosal injections or transurethral insertions of vasoactive agents, or household appliance tumescence devices in ordering to sum-up sexual relations.
Numerous placebo-controlled clinical ED studies lasting less than 1 year have documented the rubber and efficacy of sildenafil in patients with ED of various etiologies.
An unanswered subject in warmness to long-term sildenafil use is that of tachyphylaxis, a pharmacokinetic procedure in which paper sensitiveness to a drug diminishes.
A corresponding writing by El-Galley and colleagues published in 2001 reported that viagra produced tachyphylaxis, since 20% of the patients who were followed for 2 time of life needed increased dosages and 17% discontinued management because of the eventual lack of efficacy.
The results of the El-Galley domain were largely discounted upon poor follow-up; 50% of the men on sildenafil did not respond to a telecom interrogation at 2 years’ follow-up.
In direct contrast, a 3-year follow-up immersion in nerve-sparing measure prostatectomy patients (n = 41) revealed that 71% (29/41) were setup responding to the same dose of sildenafil. Of the 29% of dropouts, half (6/12) stopped because of key of spontaneous erections, with only 5 of 12 gradually losing efficacy.
Hence, most authorities have attributed loss of viagra efficacy not to tachyphylaxis, but to progress in organic disease from associated comorbidities and biological process.
However, a recent musing using cultured rat cavernosal smooth hooligan cells demonstrated molecular upregulation of the phosphodiesterase type 5 (PDE-5) enzyme when the cells treated with high doses of viagra for at least 7 days. These findings suggest that viagra is safe and effective when used at normal clinical doses and recommended dosing frequencies.
However, additional clinical investigation will be needed to evaluate the tachyphylaxis significance in chronic PDE-5 inhibitor use, especially when these agents possess long half-lives.