Tadalafil

Action-side effects
Cialis's top selling points are that it works for up to 36 hours after being swallowed and that it can be taken with or without food (Viagra works for some 4 hours). It has the same mode of action as sildenafil (Viagra), and vardenafil (Levitra).

Side effects common with theCialis medication include headache, back pain, upset stomach, and muscle aches, the last two usually coming 12–24 hours after taking the drug. These side effects usually go away after a few hours, though back pain and muscle aches may take as long as 48 hours.

Men taking nitrates or alpha blockers should not take Cialis because it could cause blood pressure problems. The company advises that in the rare event that an erection lasts for more than four hours (a condition called priapism), the man should seek emergency medical attention.