The effect of sildenafil on QT interval in healthy men

Sildenafil is widely used to treat erectile dysfunction. There have been reports of deaths in patients receiving sildenafil. In vitro sildenafil blocks the rapid component of the delayed rectifier K+ current and prolongs cardiac repolarization. We investigated the effects of sildenafil on the QT interval in vivo. Eleven healthy men received sildenafil 50mg or matching placebo in a double-blind, randomized, crossover study. A 12-lead electrocardiogram was performed before and one hour after dosing. QT intervals were measured and corrected for heart rate using the Bazett formula. Sildenafil did not alter heart rate or blood pressure. There were no significant differences in the QTc or the QT dispersion before and after sildenafil (see Table). QTc was significantly decreased after placebo by -15±6 msec (SEM) but not after sildenafil (-0.5±10 msec). We conclude that sildenafil in a mid-range therapeutic dose does not appear to increase QT interval in healthy men. However, the trend for the QTc to decrease significantly after placebo, but not after sildenafil, suggests that studies with higher doses of sildenafil should be performed. Placebo Sildenafil pre post p pre post p p QTc 409±8 394±12 0.04 408±9 408±13 0.96 ΔQTc -15±6 -0.5±10 0.33.