Generic Viagra (Sildenafil) is used for:
Treating erectile dysfunction in men. It may also be used for other conditions as determined by your doctor. Sildenafil 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 Sildenafil if:
" you are allergic to any ingredient in Sildenafil
" 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, ointment) or nitroprusside
" you use certain recreational drugs called "poppers" (eg, amyl nitrate, butyl nitrate)

Before using Sildenafil: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)
" 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 
" if you have a history of heart attack, stroke, or life-threatening irregular heartbeat, especially within the past 6 months

How to use Sildenafil:
Use Sildenafil as directed by your doctor. Check the label on the medicine for exact dosing instructions.
" An extra patient leaflet is available with Sildenafil. 
" Take Sildenafil by mouth with or without food. Sildenafil may not work as quickly if you take it with a high-fat meal.
" Sildenafil is usually taken about 1 hour before sexual activity. 
" Do not take Sildenafil more often than once daily, or as directed by your doctor.

Important safety information:
" Sildenafil may cause dizziness, drowsiness, fainting, or blurred vision. These effects may be worse if you take it with alcohol or certain medicines. 
" Patients with heart problems who take Sildenafil may be at increased risk for heart-related side effects, including heart attack or stroke. 
" Sildenafil may rarely cause a prolonged, painful erection. Contact your doctor right away if this happens.
" Do not use other medicines or treatments for erectile dysfunction while you are taking Sildenafil .
" Sildenafil does not stop the spread of HIV or other sexually transmitted diseases (STDs) to others through sexual contact.
" Sildenafil 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 Sildenafil with caution in the ELDERLY; they may be more sensitive to its effects.

Possible side effects of Sildenafil:
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.

Storage:
Store Sildenafil 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 Sildenafil out of the reach of children and away from pets.