Viagra, What is it? How to Use it? Misdose, Overdoes and Side Effects

What is Viagra?

Viagra relaxes muscles found in the walls of blood vessels and increases blood flow to particular areas of the body.

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. This page contains specific information for Viagra, not Revatio.

Do not take Viagra while also taking Revatio, unless your doctor tells you to.

Warnings About Viagra

Some medicines can cause unwanted or dangerous effects when used with Viagra. Tell your doctor about all your current medicines, especially riociguat (Adempas) and nitrates.

Do not take Viagra 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 Viagra and get emergency medical help if you have sudden vision loss.

Before taking this medicine

You should not use Viagra if you are allergic to sildenafil, or:

• if you take other medicines to treat pulmonary arterial hypertension, such as riociguat (Adempas).

• if you take nitrates.

Do not take Viagra 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 Viagra is safe for you, tell your doctor if you have ever had:

• heart disease or heart rhythm problems, coronary artery disease;

• a heart attack, stroke, or congestive heart failure;

• high or low blood pressure;

• liver or kidney disease;

• a blood cell disorder such as sickle cell anemia, multiple myeloma, or leukemia;

• a bleeding disorder such as hemophilia;

• a stomach ulcer;

• 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.

Viagra 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.

Viagra 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 medicine to anyone under 18 years old without medical advice.

How should I take Viagra?

Take Viagra exactly as it was prescribed for you. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.

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.

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.

Detailed Viagra dosage information

What happens if I miss a dose?

Since Viagra is used as needed, you are not likely to miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What to avoid

Drinking alcohol with this medicine can cause side effects.

Grapefruit and grapefruit juice may interact with sildenafil and lead to unwanted side effects. Avoid the use of grapefruit products while taking sildenafil.

Avoid using any other medicines to treat impotence, such as alprostadil or yohimbine, without first talking to your doctor.

Viagra side effects

Get emergency medical help if you have signs of an allergic reaction to Viagra: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop taking Viagra 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;

• irregular heartbeat;

• swelling in your hands, ankles, or feet;

• shortness of breath;

• seizure (convulsions); or

• a light-headed feeling, like you might pass out.

Common Viagra side effects may include:

• flushing (warmth, redness, or tingly feeling);

• headache, dizziness;

• abnormal vision (blurred vision, changes in color vision)

• runny or stuffy nose, nosebleeds;

• sleep problems (insomnia);

• muscle pain, back pain; or

• upset stomach.

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.

Viagra side effects (more detail)

What other drugs will affect Viagra?

Do not take Viagra with similar medications such as avanafil (Stendra), tadalafil (Cialis) or vardenafil (Levitra). Tell your doctor about all other medications you use for erectile dysfunction.

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;

• an antibiotic - clarithromycin, erythromycin, or telithromycin;

• antifungal medicine - ketoconazole or itraconazole; or

• medicine to treat HIV/AIDS - atazanavir, indinavir, ritonavir, or saquinavir;

• nitrates;

• medications used to treat pulmonary artery hypertension.

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.