Before using
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. DO NOT TAKE THIS 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. If you are not sure whether a certain medicine is a nitrate, contact your doctor or pharmacist. If you are currently using any of these medicines, tell your doctor or pharmacist before using sildenafil. ADDITIONAL MONITORING OF YOUR DOSE OR CONDITION may be needed if you are taking other medicines for impotence, azole antifungals (e.g., itraconazole, ketoconazole), cimetidine, erythromycin, mibefradil, rifamycins (e.g., rifampin), high blood pressure medicines, or delavirdine. 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. DO NOT START OR STOP any medicine without doctor or pharmacist approval. Inform your doctor of any other medical conditions including penis conditions (e.g., angulation, fibrosis/scarring, Peyronie's disease), history of painful/prolonged erection (priapism), sickle cell anemia, blood system cancers (e.g., leukemia or myeloma), eye problems (e.g., retina diseases like retinitis pigmentosa), kidney or liver disease, bleeding disorders, active stomach ulcers, heart problems (e.g., recent heart attack or serious arrhythmia within past 6 months, heart failure, coronary artery disease with unstable angina, aortic stenosis, idiopathic hypertrophic subaortic stenosis), recent stroke within past 6 months, very high or low blood pressure, or allergies.

Directions
Follow the directions for using this medicine provided by your doctor. 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 GRAPEFRUIT 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). Consult your doctor or pharmacist for more information. 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.

Cautions
Do NOT TAKE THIS MEDICINE if you have had an allergic reaction to it in the past or to any other ingredient that is found in it. THIS MEDICINE MAY CAUSE DIZZINESS OR VISION CHANGES. DO NOT DRIVE, OPERATE MACHINERY, OR DO ANYTHING ELSE THAT COULD BE DANGEROUS until you know how you react to this medicine. Using this medicine alone, with other medicines, or with alcohol may lessen your ability to drive or to perform other potentially dangerous tasks. TO MINIMIZE DIZZINESS OR LIGHTHEADEDNESS, sit up or stand slowly when rising from a seated or lying position. Your dose is based on your medical condition, response to therapy, and the other medicines you are taking. DO NOT EXCEED THE RECOMMENDED DOSE without checking with your doctor. Rarely, this medicine may change heart rhythm, especially if taken with other medicines that can change the heart rhythm. This change in heart rhythm can result in serious, rarely fatal, irregular heartbeats. Ask your doctor for more information and if you should stop taking any of your other medicines to reduce the risk of this side effect. BEFORE YOU BEGIN TAKING ANY NEW MEDICINE, either prescription or over-the-counter, check with your doctor or pharmacist. CAUTION IS ADVISED WHEN USING THIS MEDICINE IN THE ELDERLY because they may be more sensitive to the side effects of this medicine. THIS MEDICINE SHOULD NOT BE USED IN WOMEN OR CHILDREN.

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 notice other effects not listed above, contact your doctor, nurse, or pharmacist.

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.