WEB1 day ago · There are 4 main PDE5 drugs; Viagra (Pfizer, active drug Sildenafil, now generic) Cialis (Eli Lilly, active drug Tadalafil, now generic) Levitra (Bayer, active drug Vardenafil, now generic) and Stendra (Metuchen Pharmaceuticals, the active drug is Avanafil, not generic yet - soon).