Viagra (sildenafil) relaxes muscles 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.

USAGE:

Sildenafil comes as a tablet.
If you are taking Viagra (sildenafil) to treat erectile dysfunction, follow your doctor's directions and the guidelines in this paragraph. Take Viagra (sildenafil) as needed before sexual activity. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. Sildenafil usually should not be taken more than once every 24 hours. If you have certain health conditions or are taking certain medications, your doctor may tell you to take Viagra (sildenafil) less often. You can take sildenafil with or without food. However, if you take Viagra (sildenafil) with a high-fat meal, it will take longer for the medication to start working.
If you are taking Viagra (sildenafil) to treat PAH, follow your doctor's directions and the guidelines in this paragraph. You will probably take Viagra (sildenafil) three times a day with or without food. Take Viagra (sildenafil) at around the same times every day, and space your doses about 4 to 6 hours apart.
Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take Viagra (sildenafil) exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
If you are taking Viagra (sildenafil) for erectile dysfunction, your doctor will probably start you on an average dose of sildenafil and increase or decrease your dose depending on your response to the medication. Tell your doctor if Viagra (sildenafil) is not working well or if you are experiencing side effects.
If you are taking Viagra (sildenafil) for PAH, you should know that sildenafil controls PAH but does not cure it. Continue to take Viagra (sildenafil) even if you feel well. Do not stop taking Viagra (sildenafil) without talking to your doctor.


SIDE EFFECS:

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

Stop using sildenafil and get emergency medical help if you have sudden vision loss.
Get emergency medical help if you have any of these signs of an allergic reaction: hives, difficulty breathing swelling of your face, lips, tongue, or throat.

Stop using sildenafil and call your doctor at once if you have any of these serious side effects:

-chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling
-irregular heartbeat
-swelling in your hands, ankles, or feet
-shortness of breath
-vision changes
- feeling light-headed, fainting
-penis erection that is painful or lasts 4 hours or longer

Continue taking sildenafil and talk with your doctor if you have any of these less serious side effects:

-warmth or redness in your face, neck, or chest
-stuffy nose
- headache
-upset stomach
-back pain

Side effects other than those listed here may also occur. Talk to your doctor about any s ide effect that seems unusual or that is especially bothersome.