Viagra, also known by its generic name of sildenafil is a treatment for Erectile Dysfunction (ED), often referred to as impotence that aids men in severe getting and maintaining an erection. Viagra can be used to improve the hardness and duration of an erection. It works by affecting the response to sexual stimulation and enhancing the smooth muscle relaxant effects of nitric oxide, a chemical that is normally released in response to sexual stimulation, thus increasing blood flow into certain areas of the penis, leading to an erection.

Viagra begins to affect the body within one hour from the moment it is ingested, and can last for up to 4 hours. Most patients can take Viagra once a day as needed, and exists in 5 mg, 50 mg and 100 mg doses. Studies have show that Viagra improves erections in up to 4 of 5 men compared with 1 out of 4 who took a placebo. It is generally suggested to be taken one hour before sexual activity. Viagra is NOT approved for women.

Viagra should not be taken if you take nitrate drugs to treat angina (chest pain due to heart disease), as life risking side effects possible. Such Nitrate drugs include: Nitroglycerin (Nitrostat, Nitrolingual, Nitro-Dur, Nitro-Bid, Minitran, Deponit, Transderm-Nitro, Isosorbide dinitrate (Dilatrate-SR, Isordil, Sorbitrate), Isosorbide mononitrate (Imdur, ISMO, Monoket), Amyl nitrate or nitrite (poppers).

Common side effects may include headache, flushing, stuffy nose or runny nose mild dizziness, a rash, indigestion, upset stomach, diarrhea, and an inability to differentiate between the colors green and blue. If prolonged or severe dizziness, chest pain (including tightness, discomfort, numbness, or tingling in the chest, arms, neck, or jaw), an irregular heartbeat, swelling of the ankles or legs, or shortness of breath is experienced, seek immediate medical help at once. Rare side effects include prolonged erection (more than four hours) or painful erection. In these cases it is advised to seek medical help as well.

The following drugs can decrease the effects of Viagra: Tegretol (carbamazepine), Dilantin (phenytoin), rifamptin and rifabutin. Consult your doctor about taking Viagra if you are taking the following drugs: other drug used to treat impotence, HIV medications, antibiotic drugs, antifungal treatment.