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Uses

What is sildenafil used for?

Sildenafil is commonly used for the following conditions.

Sildenafil may also be used for other conditions as determined by your healthcare provider.

How does sildenafil work (mechanism of action)?

Sildenafil works by blocking an enzyme in the body called PDE5, which helps relax certain blood vessels. For erectile dysfunction, it increases blood flow to the penis when aroused. This makes it easier to get and keep an erection. For pulmonary arterial hypertension, sildenafil relaxes the blood vessels in the lungs. This lowers blood pressure and reduces strain on the heart.

How is sildenafil supplied (dosage forms)?

Brands and other names

  • Viagra
  • Revatio

Dosage forms and strengths

  • 10 mg/mL powder for oral suspension
  • 20 mg, 25 mg, 50 mg, 100 mg oral tablets

Sildenafil is also available in an injectable form that is usually given by a healthcare provider in a hospital or clinic.

How should I store sildenafil?

Oral Tablet. Sildenafil oral tablets should be stored at room temperature, between 68 F to 77 F (20 C to 25 C). It can be exposed to temperatures between 59 F to 86 F (15 C to 30 C) for shorter periods of time, such as when transporting it. Store in a cool, dry place.

Oral Liquid. Sildenafil oral liquid should be stored at room temperature below 86 F (30 C) or in the refrigerator, between 36 F to 46 F (2 C to 8 C). Avoid freezing. Throw away any remaining liquid 60 days after it has been mixed for you by a pharmacist or healthcare professional.

Injection Liquid. Sildenafil injection is usually given by a healthcare provider in a hospital or clinic. You will not store it at home.

Side Effects

What are the most common side effects of sildenafil?

The most common side effects of sildenafil are listed below. These side effects may vary depending on the condition that is being treated. Tell your healthcare provider if you have any of these side effects that bother you. 

  • Headache
  • Flushing
  • Upset stomach 
  • Vision changes (see below)
  • Nasal congestion
  • Pain in your muscles, back, arms, or legs
  • Nausea
  • Dizziness
  • Rash
  • Diarrhea
  • Painful, prolonged erection (see below)

There may be other side effects of sildenafil that are not listed here. Contact your healthcare provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of sildenafil?

While less common, the most serious side effects of sildenafil are described below, along with what to do if they happen.

Severe Allergic Reactions. Sildenafil may cause allergic reactions, which can be serious. Stop taking sildenafil and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Painful, Prolonged Erection (Priapism). Sildenafil may cause an unwanted erection that is persistent, painful, and that may occur without sexual arousal. Permanent damage to the penis may occur if priapism is not treated quickly. Stop taking sildenafil and get emergency help if you have any of the following symptoms of priapism.

  • Erection lasting for more than four hours
  • Erection that is unrelated to sexual stimulation
  • Painful or tender penis

Vision Changes. Sildenafil can cause mild, temporary vision changes such as seeing a blue tint, abnormal colors, blurry vision, or sensitivity to light. Though rare, some people have reported permanent vision loss. Stop taking sildenafil and get help right away if you have sudden vision loss in one or both eyes.

Hearing Loss. Sudden hearing loss has been reported after taking sildenafil. This may occur along with dizziness and ringing in the ears. Stop taking sildenafil and get help right away if you have sudden hearing loss or suddenly have trouble hearing as well as usual.

Low Blood Pressure (Hypotension). Sildenafil may cause a mild and temporary drop in blood pressure. You may be at a higher risk if you have certain health conditions or take blood pressure medicines. If you feel faint or dizzy, lie down. Tell your healthcare provider right away if you have any of the following symptoms of low blood pressure.

  • Dizziness or feeling lightheaded
  • Feeling weak or tired
  • Fainting
  • Confusion

Nosebleeds. Sildenafil may cause nosebleeds. You may be at higher risk for this if you take a blood thinner medicine. Tell your healthcare provider if you get nosebleeds often while taking sildenafil. If your nosebleed is severe or will not stop after applying pressure, get help right away. 

Warnings & Precautions

Who should not take sildenafil?

Allergies to Ingredients. People who are allergic to any of the following should not take sildenafil.

  • Sildenafil
  • Revatio
  • Viagra
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in the specific sildenafil products they stock.

Drug Interactions. Sildenafil should not be taken while you are using certain other medicines. Before taking sildenafil, tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

What should I know about sildenafil before taking it?

Do not take sildenafil unless it has been prescribed to you by a healthcare provider. Take it as prescribed.

Do not share sildenafil with other people, even if they have the same condition as you. It may harm them.

Keep sildenafil out of the reach of children. If you keep sildenafil oral liquid in a refrigerator, make sure to keep it away from children who also use the refrigerator.

Sexual activity can put extra strain on your heart, which may be unsafe for people with certain health problems, such as a recent heart attack. Talk to your healthcare provider to see if your heart is strong enough for sex. If you feel chest pain, dizziness, or nausea during sex, stop and contact your healthcare provider right away.

Sildenafil does not protect against sexually transmitted infections, including HIV.

Sildenafil belongs to a group of medicines, known as phosphodiesterase-5 (PDE-5) inhibitors, which are used to treat erectile dysfunction or pulmonary arterial hypertension. You should not take more than one PDE-5 inhibitor medicine. Medicines in this group include avanafil (Stendra), sildenafil (Viagra, Revatio, and others), tadalafil (Cialis and others), and vardenafil (Levitra, Staxyn).

Use an accurate measuring device to measure your dose of sildenafil oral liquid. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist to recommend an appropriate measuring device.

What should I tell my healthcare provider before taking sildenafil?

Tell your healthcare provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them determine if sildenafil is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your healthcare provider if you have any of the following.

  • Heart problems, such as heart rhythm problems, chest pain, or heart failure
  • Heart attack, stroke, or heart surgery within the past six months
  • Low blood pressure
  • High blood pressure that is still too high despite taking medicines for it
  • Peyronie's disease, or a penis with an abnormal curve or shape 
  • An erection lasting longer than four hours
  • A blood disorder, such as sickle cell anemia
  • An inherited eye disease called retinitis pigmentosa
  • Vision loss, or a problem with the nerve between your eyes and brain (optic nerve)
  • Health conditions or factors that raise the risk of optic nerve problems, such as diabetes, high cholesterol, smoking, being older than 50, or having a “crowded disc,” which is something an eye doctor may see in an eye exam
  • Hearing problems
  • Bleeding problems
  • Stomach ulcers
  • Liver problems
  • Severe kidney problems or dialysis
  • Pulmonary veno-occlusive disease, a condition where blood vessels in the lungs are blocked 

Pregnancy. It is not known if or how sildenafil could affect pregnancy or harm an unborn baby. Tell your healthcare provider if you are or plan to become pregnant.

Breastfeeding. Sildenafil passes into breast milk. Tell your healthcare provider if you are breastfeeding or plan to breastfeed. Your healthcare provider will advise you if you should take sildenafil while breastfeeding. 

Interactions

Does sildenafil interact with foods or drinks?

If you take sildenafil after you eat a high-fat meal, such as a burger and fries, it may take longer to start working.

Your healthcare provider may recommend limiting or avoiding grapefruit while taking sildenafil. Grapefruit or grapefruit juice can raise sildenafil levels in your body, which can increase the risk of side effects.

There are no known interactions between sildenafil and alcohol.

Does sildenafil interact with other medicines (drug interactions)?

Always tell your healthcare provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking sildenafil.

  • A nitrate, such as nitroglycerin (Nitro-Dur, Nitrostat, and others) or isosorbide, which is a medicine used for chest pain caused by a type of heart disease, or a street drug, such as amyl nitrite (“poppers”)
  • A guanylate cyclase stimulator, such as riociguat (Adempas), which is a medicine used for high blood pressure in the lungs (pulmonary arterial hypertension), or vericiguat (Verquvo), which is a medicine used for a type of heart failure
  • An alpha-blocker, such as alfuzosin (Uroxatral), doxazosin (Cardura), dutasteride, prazosin (Minipress), silodosin (Rapaflo), tamsulosin (Flomax), or terazosin (Hytrin), which is a medicine that may be used for high blood pressure and/or difficulty peeing due to an enlarged prostate
  • A blood pressure medicine, such as amlodipine (Norvasc)
  • Bosentan (Tracleer), which is a medicine used for pulmonary arterial hypertension
  • A protease inhibitor, such as ritonavir (Norvir), which is a medicine commonly used to treat HIV
  • A medicine used for fungal infections, such as ketoconazole or itraconazole (Sporanox, Tolsura)
  • Erythromycin (Ery-Tab and others) or clarithromycin (Biaxin), which is a medicine used for bacterial infections 
  • Any other medicine used for erectile dysfunction or pulmonary arterial hypertension

Some other medicines may alter the blood levels of sildenafil. Tell your healthcare provider about all medicines that you take or have recently taken.

This may not be a complete list of medicines that can interact with sildenafil. Always check with your healthcare provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much sildenafil?

If you or someone else has used too much sildenafil, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of sildenafil?

Erectile Dysfunction. For this use, sildenafil is used only when needed. Take it as your healthcare provider recommends, which is usually between 30 minutes to four hours before planned sexual activity. Do not take double or extra doses. 

Pulmonary Arterial Hypertension. For this use, take sildenafil as your healthcare provider recommends, which is usually three times a day. If you miss a dose, take it as soon as you remember. If it is almost time for your next dose, skip the missed dose and only take the next dose. Ask your healthcare provider if you are unsure what to do after a missed dose. Do not take double or extra doses.