If you are comparing Viagra vs sildenafil vs Cialis, one difference stands out immediately: Cialis usually provides the longest window of effect. Viagra and generic sildenafil contain the same active ingredient, sildenafil. Their effects can generally last for up to about four hours. Cialis contains tadalafil and can improve erectile function for up to 36 … Continue reading Viagra vs Sildenafil vs Cialis: Which ED Medicine Lasts Longer?