What is sildenafil?

Sildenafil relaxes muscles 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.

Sildenafil may also be used for other purposes not listed in this medication guide.

What is the most important information I should know about sildenafil?

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 smoke or are over 50 years old. It is not clear whether sildenafil is the actual cause of vision loss.

What should I discuss with my healthcare provider before taking sildenafil?

Before taking sildenafil, tell your doctor if you are allergic to any drugs, or if you have:

• heart disease or heart rhythm problems;

• a recent history (in the past 6 months) of a heart attack, stroke, or heart rhythm disorder;

• congestive heart failure;

• high or low blood pressure;

• coronary artery disease;

• liver disease;

• 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.

If you have any of these conditions, you may need a dose adjustment or special tests to safely take sildenafil.

How should I take sildenafil?

Take sildenafil exactly as it was prescribed for you. Do not take it in larger doses or for longer than recommended by your doctor. Follow the directions on your prescription label.

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.

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.

What happens if I miss a dose?

Viagra is used as needed, so you are not likely to be on a dosing schedule.

If you miss a dose of Revatio, take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at the next regularly scheduled time. Do not take extra medicine to make up the missed dose.

What happens if I overdose?

What should I avoid while taking sildenafil?

Sildenafil side effects

Stop using sildenafil and call your doctor at once if you have any of these serious side effects:

• sudden vision loss;

• ringing in your ears, or sudden hearing loss;

• chest pain or heavy feeling, pain spreading to the arm or shoulder, nausea, sweating, general ill feeling;

• irregular heartbeat;

• swelling in your hands, ankles, or feet;

• shortness of breath;

• vision changes;

• feeling light-headed, fainting; or

• penis erection that is painful or lasts 4 hours or longer.

Less serious side effects may include:

• warmth or redness in your face, neck, or chest;

• stuffy nose;

• headache;

• upset stomach; or

• back pain.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

What other drugs will affect sildenafil?

Before taking sildenafil, tell your doctor about all other medications you use for erectile dysfunction, or if you are using any of the following medications:

• bosentan (Tracleer);

• a blood thinner such as warfarin (Coumadin);

• cimetidine (Tagamet, Tagamet HB);

• an antibiotic such as erythromycin (E-Mycin, Eryc, Ery-Tab) or clarithromycin (Biaxin);

• doxazosin (Cardura), prazosin (Minipress), Terazosin (Hytrin);

• HIV medicines such as amprenavir (Agenerase), tipranavir (Aptivus), darunavir (Prezista), efavirenz (Sustiva), nevirapine (Viramune), indinavir (Crixivan), saquinavir (Invirase, Fortovase), lopinavir/ritonavir (Kaletra), fosamprenavir (Lexiva), ritonavir (Norvir), atazanavir (Reyataz), or nelfinavir (Viracept);

• an antifungal medication such as itraconazole (Sporanox) or ketoconazole (Nizoral);

• carbamazepine (Tegretol), phenobarbital (Luminal), or phenytoin (Dilantin); or

• rifampin (Rifadin, Rimactane) or rifabutin (Mycobutin).

This list is not complete and there may be other drugs that can interact with sildenafil. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor.

Where can I get more information?

• Your pharmacist can provide more information about sildenafil.