Medically reviewed on October 12, 2017.
What is sildenafil?
Sildenafil relaxes muscles of the blood vessels 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.
Do not take Viagra while also taking Revatio, unless your doctor tells you to.
Sildenafil may also be used for purposes not listed in this medication guide.
Do not take sildenafil if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, and some recreational drugs such as "poppers". Taking sildenafil with a nitrate medicine can cause a sudden and serious decrease in blood pressure.
Contact your doctor or seek emergency medical attention if your erection is painful or lasts longer than 4 hours. A prolonged erection (priapism) can damage the penis.
Stop using sildenafil and get emergency medical help if you have sudden vision loss.
Before taking this medicine
You should not use sildenafil if you are allergic to it, or:
if you take other medicines to treat pulmonary arterial hypertension, such as riociguat (Adempas).
Do not take sildenafil if you are also using a nitrate drug for chest pain or heart problems. This includes nitroglycerin, isosorbide dinitrate, and isosorbide mononitrate. Nitrates are also found in some recreational drugs such as amyl nitrate or nitrite ("poppers"). Taking sildenafil with a nitrate medicine can cause a sudden and serious decrease in blood pressure.
To make sure sildenafil is safe for you, tell your doctor if you have ever had:
heart disease or heart rhythm problems, coronary artery disease;
high or low blood pressure;
liver or kidney disease;
retinitis pigmentosa (an inherited condition of the eye);
a physical deformity of the penis (such as Peyronie's disease); or
if you have been told you should not have sexual intercourse for health reasons.
Sildenafil can decrease blood flow to the optic nerve of the eye, causing sudden vision loss. This has occurred in a small number of people taking sildenafil, most of whom also had heart disease, diabetes, high blood pressure, high cholesterol, or certain pre-existing eye problems, and in those who smoked or were over 50 years old. It is not clear whether sildenafil is the actual cause of vision loss.
This medicine is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
It is not known whether sildenafil passes into breast milk or if it could harm a nursing baby. Tell your doctor if you are breast-feeding a baby.
Do not give this medication to anyone under 18 years old without medical advice.
How should I take oral sildenafil?
Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Revatio is usually taken three times each day, about 4 to 6 hours apart.
Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. You may take it up to 4 hours before sexual activity. Do not take Viagra more than once per day.
Shake the oral suspension (liquid) well just before you measure a dose. Measure liquid medicine with the dosing syringe provided, or with a special dose-measuring spoon or medicine cup. If you do not have a dose-measuring device, ask your pharmacist for one.
Viagra can help you have an erection when sexual stimulation occurs. An erection will not occur just by taking a pill. Follow your doctor's instructions.
During sexual activity, if you become dizzy or nauseated, or have pain, numbness, or tingling in your chest, arms, neck, or jaw, stop and call your doctor right away. You could be having a serious side effect of sildenafil.
Store at room temperature away from moisture and heat.
What happens if I miss a dose?
Since Viagra is used as needed, you are not likely to miss a dose.
If you miss a dose of Revatio, take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.
What should I avoid while taking oral sildenafil?
Drinking alcohol with this medicine can cause side effects.
Oral sildenafil side effects
Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop taking sildenafil and get emergency medical help if you have:
heart attack symptoms--chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating;
vision changes or sudden vision loss; or
erection is painful or lasts longer than 4 hours (prolonged erection can damage the penis).
Call your doctor at once if you have:
ringing in your ears, or sudden hearing loss;
swelling in your hands, ankles, or feet;
shortness of breath;
seizure (convulsions); or
a light-headed feeling, like you might pass out.
Common side effects may include:
flushing (warmth, redness, or tingly feeling);
abnormal vision (blurred vision, changes in color vision)
runny or stuffy nose, nosebleeds;
sleep problems (insomnia);
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
Sildenafil dosing information
Usual Adult Dose for Erectile Dysfunction:
Initial dose: 50 mg orally once a day, as needed, 1 hour prior to sexual activity
Maintenance: 25 to 100 mg orally once a day, as needed, 1 hour prior to sexual activity
Comments: This drug may be taken anywhere from 30 minutes to 4 hours before sexual activity.
Use: Treatment of erectile dysfunction
Usual Adult Dose for Pulmonary Hypertension:
-Initial dose: 5 or 20 mg orally three times a day, 4 to 6 hours apart
-Maximum dose: 20 mg orally three times a day
-Initial dose: 2.5 or 10 mg IV bolus three times a day
-No greater efficacy was achieved with oral doses higher than the maximum recommended dose.
-A 10 mg injection dose is predicted to provide pharmacological effect equivalent to the 20 mg oral dose.
Use: Treatment of PAH (WHO Group I) in adults to improve exercise ability and delay clinical worsening
Usual Geriatric Dose for Erectile Dysfunction:
Initial dose: 25 mg orally once a day 1 hour prior to sexual activity
Use: Treatment of erectile dysfunction
What other drugs will affect oral sildenafil?
Tell your doctor about all your current medicines and any you start or stop using, especially:
drugs to treat high blood pressure or a prostate disorder;
This list is not complete. Other drugs may interact with sildenafil, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.
Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Copyright 1996-2018 Cerner Multum, Inc. Version: 12.01.
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