In fixed-dose studies, the incidence of some adverse effects increased with dose. The nature of the adverse effects in flexible-dose studies, which more closely reflect the recommended dosage regimen was similar to that for fixed-dose studies. At doses above the recommended range, adverse events were similar to those detailed previously but generally were reported more frequently.
Special Patient Groups: Healthy elderly volunteers (≥65 years) had a reduced clearance of Sildenafil, with free plasma concentrations approximately 40% greater than those seen in healthy younger volunteers (18-45 years). A pooled analysis of a large number of studies showed that age had no clinically important effect on the incidence of adverse effects.
Toxicology: No evidence of drug-related carcinogenicity was seen in a 24-month study in rats subjected to doses of up to 42x the maximum recommended human dose (MRHD) on a mg/kg basis and approximately 5x the MRHD on a mg/m2 basis. In an 18 to 21-month study in mice subjected to doses up to 21x the MRHD on a mg/kg basis (approximately 2x the MRHD on a mg/m2 basis), bacterial and in vivo mutagenicity tests were negative. There was no effect on sperm motility or morphology after single 100-mg oral doses of Sildenafil in healthy volunteers. No teratogenic effects, impairment of fertility or adverse effects on peri-/postnatal development were found in reproduction studies in animal studies (on rats and rabbits) following oral administration of Sildenafil.
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