Viagra is used for:
Treating erectile dysfunction (ED). It may also be used for other conditions as determined by your doctor. Viagra is a phosphodiesterase inhibitor. It works by helping to increase blood flow into the penis during sexual stimulation. This helps you to achieve and maintain an erection.

Do NOT use Viagra if:
• you are allergic to any ingredient in Viagra
• you have been advised by your doctor to avoid sexual activity because of heart problems
• you are taking nitrates (eg, isosorbide, nitroglycerin) in any form (eg, tablet, capsule, patch, ointment) or nitroprusside
• you use certain recreational drugs called "poppers" (eg, amyl nitrate, butyl nitrate)
Contact your doctor or health care provider right away if any of these apply to you.

Before using Viagra:
Some medical conditions may interact with Viagra . Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:
• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
• if you have allergies to medicines, foods, or other substances
• if you have a deformed penis (eg, Peyronie disease, cavernosal fibrosis), blood problems (eg, sickle cell anemia, leukemia, multiple myeloma), or any other condition that may increase the risk of a prolonged erection (eg, priapism)
• if you have a history of certain eye problems (eg, retinitis pigmentosa, sudden vision loss, optic neuropathy, macular degeneration)
• if you have a history of liver or kidney problems, high or low blood pressure, ulcers, bleeding problems, heart problems (eg, heart failure, irregular heartbeat, aortic stenosis, angina), or blood vessel problems
• if you have a history of heart attack, stroke, or life-threatening irregular heartbeat, especially within the past 6 months
Some MEDICINES MAY INTERACT with Viagra . Tell your health care provider if you are taking any other medicines, especially any of the following:
• Alpha-blockers (eg, doxazosin), amlodipine, medicines for high blood pressure, nitrates (eg, isosorbide, nitroglycerin), or nitroprusside because severe low blood pressure with dizziness, lightheadedness, and fainting may occur
• Azole antifungals (eg, itraconazole), cimetidine, H2 agonists (eg, famotidine), HIV protease inhibitors (eg, ritonavir), macrolide antibiotics (eg, erythromycin), or telithromycin because they may increase the risk of Viagra 's side effects
• Bosentan or rifampin because they may decrease Viagra 's effectiveness
This may not be a complete list of all interactions that may occur. Ask your health care provider if Viagra may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Viagra:
Use Viagra as directed by your doctor. Check the label on the medicine for exact dosing instructions.
• An extra patient leaflet is available with Viagra . Talk to your pharmacist if you have questions about this information.
• Take Viagra by mouth with or without food. Viagra may not work as quickly if you take it with a high-fat meal.
• Viagra is usually taken about 1 hour before sexual activity. However, it may be taken anywhere from 4 hours to ? hour before sexual activity. Talk with your doctor about the best way to take Viagra.
• Do not take Viagra more often than once daily, or as directed by your doctor.
• If you miss a dose of Viagra and you still intend to engage in sexual activity, take it as soon as you remember. Continue to take it as directed by your doctor.
Ask your health care provider any questions you may have about how to use Viagra.
Important safety information:
• Viagra may cause dizziness, drowsiness, fainting, or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. Use Viagra with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.
• Viagra may cause dizziness, lightheadedness, or fainting; alcohol, hot weather, exercise, or fever may increase these effects. To prevent them, sit up or stand slowly, especially in the morning. Sit or lie down at the first sign of any of these effects.
• Patients with heart problems who take Viagra may be at increased risk for heart-related side effects, including heart attack or stroke. Symptoms of a heart attack may include chest, shoulder, neck, or jaw pain; numbness of an arm or leg; severe dizziness, headache, nausea, stomach pain, or vomiting; fainting; or vision changes. Symptoms of a stroke may include confusion, vision or speech changes, one-sided weakness, or fainting. Contact your doctor or seek medical attention right away if you experience these symptoms.
• Viagra may rarely cause a prolonged, painful erection. This could happen even when you are not having sex. If this is not treated right away, it could lead to permanent sexual problems such as impotence. Contact your doctor right away if this happens.
• Do not use other medicines or treatments for erectile dysfunction while you are taking Viagra .
• Viagra does not stop the spread of HIV or other sexually transmitted diseases (STDs) to others through sexual contact. Use barrier methods of birth control (eg, condoms) if you have HIV infection or an STD.
• Viagra will not prevent pregnancy. If your partner may become pregnant and you wish to avoid pregnancy, be sure to use an effective form of birth control.
• Use Viagra with caution in the ELDERLY; they may be more sensitive to its effects.
• Viagra is not recommended for use in CHILDREN; safety and effectiveness in children have not been confirmed.
Possible side effects of Viagra:
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:
• Diarrhea; dizziness; flushing; headache; heartburn; mild, temporary vision changes (eg, blurred vision, sensitivity to light, blue/green color tint to vision); stuffy nose; upset stomach.
Seek medical attention right away if any of these SEVERE side effects occur:
• Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fainting; fast or irregular heartbeat; painful or prolonged erection; ringing in the ears; seizure; severe or persistent dizziness; severe or persistent vision changes; sudden decrease or loss of vision in one or both eyes; sudden hearing loss.
This is not a complete list of all side effects that may occur.

Proper storage of Viagra:
Store Viagra at 77 degrees F (25 degrees C). Brief storage at temperatures between 59 and 86 degrees F (15 and 30 degrees C) is permitted. Store away from heat, moisture, and light. Do not store in the bathroom. Keep Viagra out of the reach of children and away from pets.