The proportion of responders was calculated for the sildenafil and placebo treatment groups and was analysed Study II using the Mainland-Gart test for treatment effect. When daily testosterone was given, subsequent sildenafil Viagra use resulted in IIEF the International Index of Erectile Function questionnaire used to determine erectile function scores improving significantly. It will not spontaneously cause an erection. Patients’ self-assessments of total mean durations of grade 3 and 4 erections were analysed using an analysis of variance anova model appropriate for a two-treatment, two-period crossover design Study I. General Health A holistic approach to health is important to maximize the effectiveness of Viagra, and it may even help your sexual performance without Viagra use. Selectivity is the ability of the drug to attach to the specific enzyme PDE 5 found in penile tissues. Other common side effects include headache, flushing, dyspepsia or bloating, abnormal vision, and stuffy nose or cold-like symptoms.Sildenafil Tablets (Erectile Dysfunction) Generic name: Sildenafil Tablets (Erectile Dysfunction) [ sil-DEN-a-fil ] Brand name: Viagra. Drug classes: Agents for pulmonary hypertension, Impotence agents. Medically reviewed by Last updated on As a result, many will turn to Viagra (sildenafil) as a quick, effective solution for their ED. Viagra can last for about four hours or more in some people and should be taken 30 minutes to an hour before sexual activity. This article will discuss Viagra’s ability to work quickly, its current safety concerns, alternative treatments, and more. Sildenafil (Viagra) has a half-life of 4 hours and vardenafil (Levitra) has a half-life of hours while tadalafil (Cialis) has a half-life of hours. This means that vardenafil (Levitra) should act longer than sildenafil (Viagra) but the clinical significance is not known. Tadalafil (Cialis) has the longest half-life and allows you to.