Sildenafil relaxes muscles of the blood vessels and increases blood flow to particular areas of the body. Sildenafil under the name Viagra is used to treat erectile dysfunction (impotence) in men. Another brand of sildenafil is Revatio, which is used to treat pulmonary arterial hypertension and improve exercise capacity in men and women. Do not take sildenafil if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, and some recreational drugs such as "poppers". Taking sildenafil with a nitrate medicine can cause a sudden and serious decrease in blood pressure. Some medicines can cause unwanted or dangerous effects when used with sildenafil. Tell your doctor about all your current medicines, especially riociguat (Adempas). 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. The most common medications used to treat erectile dysfunction (ED) are Viagra, Cialis, Sildenafil, and Levitra. They belong to a class of drugs called phosphodiesterase 5 inhibitors (PDE5 inhibitors), which will be explained below. An erection occurs when someone is stimulated by an erotic thought or sexual contact. That leads to a series of chemical reactions in the blood vessels of the penis that results in 6 times the blood flow getting trapped in the penis. An erection might last indefinitely if it weren’t for chemicals called phosphodiesterases. They work at reversing the process that keeps the penis erect. Usually there is a balance between the chemicals that cause an erection and those that would return the penis to being flaccid. They pull in opposite directions with one dominating over the other in a perfect sequence that lets a man have an erection as long as it is needed.
VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. Each tablet contains 25 mg, 50 mg or 100 mg of sildenafil as citrate. Excipient with known effect Lactose monohydrate. 1 mg per 25 mg tablet. 2 mg per 50 mg.