The main efficacy and action of tadalafil is to treat erectile dysfunction in men. Tadalafil tablets are cyclic guanosine monophosphate specific phosphodiesterase inhibitors that cause smooth muscle relaxation and blood flow into the penile tissue to produce an erection. Widely used clinically to treat erectile dysfunction in men, it is an as-needed medication that is usually used about 2 hours before sexual intercourse. The use of tadalafil may cause adverse reactions such as headache, back pain, and indigestion. Tadalafil is contraindicated in people who are allergic to any of the ingredients in this product, patients who are taking any form of nitrates, guanylate cyclase stimulators, women, children and other people. Tadalafil is a prescription drug and should be used in strict accordance with medical advice.