Cialis (tadalafil) relaxes muscles and increases blood flow to particular areas of the body.

Cialis is used to treat erectile dysfunction (impotence) in men. Adcirca, another brand of tadalafil, is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women.

Cialis may also be used for purposes other than those listed in this medication guide.

Most important: Do not take Cialis if you are allergic to tadalafil, or if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin (Nitrostat, Nitrolingual, Nitro-Dur, Nitro-Bid, Minitran, Deponit, Transderm-Nitro), isosorbide dinitrate (Dilatrate-SR, Isordil, Sorbitrate), and isosorbide mononitrate (Imdur, ISMO, Monoket), or recreational drugs such as amyl nitrate or nitrite (“poppers”). Taking Cialis with a nitrate can cause a serious decrease in blood pressure, leading to fainting, stroke, or heart attack.

If you become dizzy or nauseated during sexual activity, or if you have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be suffering from a serious side effect of this medicine.

Do not take Cialis more than once a day. Allow 24 hours to pass between doses. Contact your doctor or seek emergency medical attention if your erection is painful or lasts longer than 4 hours. A prolonged erection (priapism) can damage the penis.

Cialis can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking Cialis, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoke or are over 50 years old. It is not clear whether Cialis is the actual cause of vision loss.

Stop using Cialis and get emergency medical help if you have sudden vision loss.