Viagra ® (Brand)

Common uses
This medicine is a phosphodiesterase inhibitor used to treat sexual function problems such as impotence or erectile dysfunction. In combination with sexual stimulation, this medicine works by helping the blood flow into the penis to achieve and maintain an erection.

Before using
Do not take his medicine if you are also taking or using nitroglycerin, (e.g., tablet, patch, or ointment dose forms) or other nitrates (e.g., isosorbide), nitroprusside (or any \'nitric oxide donor\' medicine), or recreational drugs called \'poppers\' containing amyl or butyl nitrate because very serious interactions may occur.

Mechanism of action

Part of the physiological process of erection involves the parasympathetic nervous system causing the release of nitric oxide (NO) in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries, resulting in increased inflow of blood and an erection.

If you are taking an HIV protease inhibitor (e.g., ritonavir, saquinavir), do not take more than a 25 mg dose of sildenafil in a 48-hour period. If you are taking more than a 25 mg dose of sildenafil and are also taking an alpha-blocker medicine (e.g., doxazosin, prazosin, terazosin) for various conditions (e.g., enlarged prostate), separate the time between taking these medicines by more than 4 hours. See How To Use section for drug-food interaction information.


Directions
Take this medicine by mouth as needed between four hours and one-half hour before sexual activity (about 1 hour before is most effective); or take as directed by your doctor. Do not take this medicine more often than once daily as needed. A high fat meal may delay the time of onset of this medicine.

Avoid eating grapefruit or drinking grapefruin juice while being treated with this medicine unless your doctor instructs you otherwise. Your dosage is based on your medical condition, your response to therapy, and other medicines you are taking (see also Before Using section).

Store this medicine at room temperature 77 degrees F (25 degrees C) in a tightly-closed container, away from heat, moisture, and light. Brief storage between 59 and 86 degrees F (15 and 30 degrees C) is permitted.



Possible side effects
Side effects that may occur while taking this medicine include headache, flushing, stomach upset, heartburn, nasal stuffiness, diarrhea, dizziness, or lightheadedness. Vision changes such as increased sensitivity to light, blurred vision, or impaired blue/green color discrimination may also occur. If these continue or are bothersome, check with your doctor or pharmacist.

Sexual activity may put extra strain on your heart, especially if you have heart problems, if you have heart problems and experience any serious side effects while having sex, stop having sex and tell your doctor immediately. These side effects include severe dizziness, fainting, chest pain, or nausea. In the unlikely event that you have a painful or prolonged erection (lasting more than 4 hours), stop using this medicine and seek immediate medical attention or permanent problems could occur.

An allergic reaction to this medicine is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include rash, itching, unusual swelling, severe dizziness, or trouble breathing.

If you take too much
If overdose is suspected, contact your local poison control center or emergency room immediately. Symptoms of overdose may include severe dizziness, fainting, or prolonged erection.

Additional information
If your symptoms do not improve or if they become worse, check with your doctor. Do not share this medicine with others for whom it was not prescribed, since they may have a problem that is not effectively treated with this medicine, or they may have a condition that is complicated by this medicine.

Do not use this medicine for other health conditions. Keep this medicine out of the reach of children and pets. If using this medicine for an extended period of time, obtain refills before your supply runs out.

Drug interactions
Drug interactions can result in unwanted side effects or prevent a medicine from doing its job. Some medicines or medical conditions may interact with this medicine. Inform your doctor or pharmacist of all prescription and over-the-counter medicine that you are taking.