Mutagenesis Sildenafil was negative in in vitro bacterial and Chinese hamster ovary cell assays to detect mutagenicity, and in vitro human lymphocytes and in vivo mouse micronucleus assays to detect clastogenicity. The titration studies, in which most patients received mg, showed similar results. The primary endpoint was time to limiting angina in the evaluable cohort. The primary measure in the principal studies was a sexual function questionnaire the International Index of Erectile Function – IIEF administered during a 4-week treatment-free run-in period, at baseline, at follow-up visits, and at the end of double-blind, placebo-controlled, at-home treatment. The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range.In general, a lower dose (5mg) that’s meant for daily use can cost around $20 to $32 per dose, and a higher dose (10mg and 20mg) meant for “as-needed” use can cost around $80 – $85 per dose. Cialis is not covered by most Medicare and insurance plans, but manufacturer and pharmacy coupons can help offset the cost. More Info See Prices. Viagra (sildenafil) as . Viagra costs around $60–$70 per tablet. Generic sildenafil can range from $2–$18 per pill, depending on the manufacturer and dose. Who makes generic Viagra?