Sildenafil | Side Effects, Dosage, Uses & More
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Generic Name:

sildenafil, Oral tablet

All Brands

  • Viagra
SECTION 1 of 5

Highlights for sildenafil

Oral tablet
1

Sildenafil is used to treat pulmonary arterial hypertension (PAH). This condition causes high blood pressure in your lungs. Sildenafil slows down the worsening of your illness. It also makes you more able to exercise.

2

This drug comes in the form of a tablet and suspension (liquid) you take by mouth. It also comes as an injection that’s only given by a doctor.

3

Sildenafil is available as a brand-name drug called Revatio. It’s also available as a generic drug.

4

The more common side effects of this drug include nosebleeds, headaches, upset stomach, or flushing (reddening and warming of the face). They also include trouble sleeping, fever, or erections that last longer than normal.

5

In some cases, sildenafil can cause serious side effects. These can include sudden vision loss, hearing loss, or an erection lasting more than 4 hours.

IMPORTANT INFORMATION

Priapism (an erection that won’t go away)

This drug can cause an erection that won’t go away. If you have an erection that lasts more than 4 hours, call 9-1-1 or go to the nearest emergency room. If it’s not treated right away, this condition can cause permanent damage to your penis.

Sudden vision loss

This drug may cause sudden vision loss in one or both eyes. This can be a sign of a serious eye problem. If this occurs, stop taking this drug and call your doctor right away.

Sudden hearing loss

This drug may cause hearing loss, tinnitus (ringing in your ears), or dizziness. If you have sudden hearing loss with or without tinnitus or dizziness, stop taking this drug and call your doctor right away.

Not for use in children

Children with PAH who take this drug may be at increased risk of death. Children should not take sildenafil.

What is sildenafil?

Sildenafil is a prescription drug. It comes in the form of a tablet and suspension (liquid). Both are taken by mouth. This drug is also available in an intravenous (IV) form, which is only given by a doctor.

Sildenafil is available as a brand-name drug called Revatio. It’s also available as a generic drug. Generic drugs usually cost less. In some cases, they may not be available in every strength or form as the brand-name version. Talk to your doctor to see if the generic version will work for you.

Why it's used

This drug is used to treat pulmonary arterial hypertension (PAH) in adults. With this condition, the blood pressure in your lungs is too high. Your heart has to work very hard to pump blood into your lungs. 

This drug slows down how fast your illness worsens. It also makes you more able to exercise.

How it works

This drug belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. A class of drugs is a group of medications that work in a similar way. These drugs are often used to treat similar conditions.

This drug works by relaxing the muscles and opening up the blood vessels in your lungs. This decreases the blood pressure in your lungs.

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SECTION 2 of 5

sildenafil Side Effects

Oral tablet

More Common Side Effects

The more common side effects of sildenafil can include:

  • nosebleeds

  • headaches

  • upset stomach

  • flushing (reddening and warming of the face)

  • trouble sleeping

  • fever

  • an erection that lasts longer than normal

  • respiratory infection

  • nausea

  • vomiting

  • bronchitis

  • pharyngitis (sore throat)

  • runny nose

If these effects are mild, they may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk to your doctor or pharmacist.

Serious Side Effects

Call your doctor right away if you have serious side effects. Call 9-1-1 if your symptoms feel life-threatening or if you think you’re having a medical emergency. Serious side effects and their symptoms can include the following:

  • Low blood pressure. Symptoms can include:

    • blurry vision
    • confusion
    • dizziness
    • fainting
    • lightheadedness
    • nausea or vomiting
    • sleepiness
    • weakness
  • Increased shortness of breath or trouble breathing

  • Priapism (an erection that won’t go away). Symptoms can include:

    • an erection that lasts more than 4 hours
  • Vision problems. Symptoms can include:

    • sudden vision loss in one or both eyes
  • Hearing problems. Symptoms can include:

    • sudden hearing loss
    • tinnitus (ringing in your ears)
    • dizziness
  • Heart problems, such as heart attack, stroke, or irregular heart rate. Symptoms can include:

    • chest pain
    • shortness of breath
    • dizziness
    • trouble speaking
    • confusion
    • nausea or vomiting
    • feeling lightheaded
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

Sildenafil doesn’t cause drowsiness.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this information includes all possible side effects. This information is not a substitute for medical advice. Always discuss possible side effects with a healthcare provider who knows your medical history.
SECTION 3 of 5

sildenafil May Interact with Other Medications

Oral tablet

Sildenafil can interact with other medications, vitamins, or herbs you may be taking. An interaction is when a substance changes the way a drug works. This can be harmful or prevent the drug from working well. 

To help avoid interactions, your doctor should manage all of your medications carefully. Be sure to tell your doctor about all medications, vitamins, or herbs you’re taking. To find out how this drug might interact with something else you’re taking, talk to your doctor or pharmacist.

Alcohol interaction

The use of drinks that contain alcohol raises your risk of low blood pressure from this drug. If you drink alcohol, talk to your doctor. You may need to have your blood pressure monitored.

Medications that might interact with this drug

Drugs you should not use with sildenafil

Do not take these drugs with sildenafil. Doing so can cause dangerous effects in the body. Examples of these drugs include:

  • Nitrates, such as isosorbide mononitrate, isosorbide dinitrate, or nitroglycerin. 
    • Taking these drugs with sildenafil can cause your blood pressure to drop suddenly to an unsafe level. 
  • Guanylate cyclase stimulators, such as riociguat. 
    • Taking these drugs with sildenafil can cause your blood pressure to drop suddenly to an unsafe level.

Interactions that increase your risk of side effects

Side effects from sildenafil: Taking sildenafil with certain medications raises your risk of side effects from sildenafil. This is because the amount of sildenafil in your body is increased. Examples of these drugs include: 

  • Human immunodeficiency virus (HIV) drugs, such as ritonavir, indinavir, saquinavir, or atazanavir. 
    • Increased side effects can include low blood pressure, dizziness, or vision problems. They can also include erections that last longer than normal.
  • Certain antibiotics, such as clarithromycin, telithromycin, or erythromycin.
    • Increased side effects can include low blood pressure, dizziness, or vision problems. They can also include erections that last longer than normal.
  • Certain antifungals, such as ketoconazole or itraconazole.
    • Increased side effects can include low blood pressure, dizziness, or vision problems. They can also include erections that last longer than normal.

Side effects from other drugs: Taking sildenafil with certain medications raises your risk of side effects from these drugs. Examples of these drugs include:

  • Alpha-blockers, such as terazosin, tamsulosin, doxazosin, alfuzosin, or silodosin.
    • Increased side effects can include a drop in blood pressure, or fainting. 
  • Blood pressure drugs, such as amlodipine.
    • Increased side effects can include blood pressure that’s too low.
  • Drugs for erectile dysfunction, such as avanafil, tadalafil, or vardenafil.
    • Increased side effects can include low blood pressure or erections that last longer than normal.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs interact differently in each person, we cannot guarantee that this information includes all possible interactions. This information is not a substitute for medical advice. Always speak with your healthcare provider about possible interactions with all prescription drugs, vitamins, herbs and supplements, and over-the-counter drugs that you are taking.
Sildenafil warnings
heart problems
People with heart problems

This drug can lower your blood pressure. If you’ve had certain heart problems in the last 6 months, ask your doctor whether this drug is safe for you. These problems include a heart attack, stroke, or life-threatening heart rhythm problem. Also talk with your doctor if you have a low or high resting blood pressure, or a history of heart failure or coronary artery disease.

pulmonary veno-occlusive disease
People with pulmonary veno-occlusive disease (PVOD)

If you have PVOD, taking this drug may worsen your heart function. You should not take this drug.

eye problems
People with eye problems

This drug may cause sudden loss of vision in one or both eyes. This may be a sign of non-arteritic anterior ischemic optic neuropathy (NAION). If you’ve already had NAION or have crowded optic disc, you may have a higher risk of NAION and vision changes with this drug.

problems with the shape of their penis
People with problems with the shape of their penis

If you have a problem with the shape of your penis, such as Peyronie’s disease, this drug raises your risk of having an erection that lasts more than 4 hours.

stomach ulcers or bleeding
People with a history of stomach ulcers or bleeding

This drug raises your risk of stomach bleeding, ulcers, or small holes in the lining of your digestive system. These events can be fatal (cause death). They can happen at any time, with or without symptoms.

sickle cell anemia
People with sickle cell anemia

This drug may cause a common painful complication of sickle cell anemia called vaso-occlusive crisis. If you have sickle cell anemia, ask your doctor whether this drug is safe for you.

pregnant women
Pregnant women

This drug is a category B pregnancy drug. That means two things: 

  1. Research in animals has not shown a risk to the fetus when the mother takes the drug.
  2. There aren’t enough studies done in humans to show if the drug poses a risk to the fetus.

Talk to your doctor if you’re pregnant or planning to become pregnant. It appears unlikely that this drug will harm a fetus. However, this drug should only be used during pregnancy if clearly needed.

breast-feeding
Women who are breast-feeding

This drug may pass into breast milk and may cause side effects in a child who is breast-fed.

Talk to your doctor if you breast-feed your child. You may need to decide whether to stop breast-feeding or stop taking this medication.

seniors
For seniors

The kidneys, liver, or heart of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

children
For children

This drug isn’t recommended in children younger than 18 years of age. In one study, children with pulmonary arterial hypertension (PAH) who took this drug had an increased chance of death.

call the doctor
When to call the doctor

Call your doctor if you become pregnant while taking this drug.

allergies
Allergies

This drug can cause a severe allergic reaction. Symptoms can include: 

  • trouble breathing
  • swelling of your throat or tongue 

If you have an allergic reaction, call your doctor or local poison control center right away. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room. 

Don’t take this drug again if you’ve ever had an allergic reaction to it. Taking it again could be fatal (cause death).

SECTION 4 of 5

How to Take sildenafil (Dosage)

Oral tablet

All possible dosages and drug forms may not be included here. Your dosage, drug form, and how often you take the drug will depend on:

  • your age
  • the condition being treated
  • how severe your condition is
  • other medical conditions you have
  • how you react to the first dose

What are you taking this medication for?

Pulmonary arterial hypertension (PAH)

Brand: Revatio

Form: Oral tablet
Strengths: 20 mg
Form: Oral suspension
Strengths: 10 mg/mL

Generic: sildenafil

Form: Oral tablet
Strengths: 20 mg
Adult dosage (ages 18–64 years)
  • Typical dosage: 5 or 20 mg, taken 3 times per day.
  • Maximum dosage: 20 mg, taken 3 times per day.
Child dosage (ages 0–17 years)

This drug shouldn’t be used in people younger than 18 years of age.

Senior dosage (ages 65 years and older)

The kidneys, liver, or heart of older adults may not work as well as they used to. This can cause your body to process drugs more slowly. As a result, more of a drug stays in your body for a longer time. This raises your risk of side effects.

Your doctor may start you on a lowered dose of sildenafil. This can help keep levels of this drug from building up in your body.

Disclaimer: Our goal is to provide you with the most relevant and current information. However, because drugs affect each person differently, we cannot guarantee that this list includes all possible dosages. This information is not a substitute for medical advice. Always to speak with your doctor or pharmacist about dosages that are right for you.
Pharmacist's Advice
Clinical Associate Professor, University of Illinois at Chicago College of Pharmacy

This drug comes with serious risks if you don’t take it as prescribed.

If you stop taking the drug suddenly or don’t take it at all

Your condition won’t improve, and may get worse. Also, you won’t be able to exercise. 

If you miss doses or don’t take the drug on schedule

Your medication may not work as well or may stop working completely. For this drug to work well, a certain amount needs to be in your body at all times.

If you take too much

You could have dangerous levels of the drug in your body. Symptoms of an overdose of this drug can include:

  • low blood pressure
  • fainting
  • dizziness
  • vision problems
  • hearing problems
  • upset stomach
  • chest pain

If you think you’ve taken too much of this drug, call your doctor or local poison control center. If your symptoms are severe, call 9-1-1 or go to the nearest emergency room right away.

What to do if you miss a dose

Take your dose as soon as you remember. But if you remember just a few hours before your next scheduled dose, take only one dose. Never try to catch up by taking two doses at once. This could result in dangerous side effects.

How to tell if the drug is working

You’ll be able to exercise more easily. Your doctor will also check you to decide if this drug is working.

This drug is used for long-term treatment.

Important considerations for taking sildenafil
take this drug with or without food
You can take this drug with or without food
timing
Take this drug 3 times per day about 4–6 hours apart. Take it at the same times every day
can cut or crush
You can cut or crush the tablet
storage
Store this drug carefully
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medication is refillable
A prescription for this medication is refillable
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Travel
Travel
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Clinical monitoring
Clinical monitoring
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not usually stocked
Not every pharmacy stocks this drug. When filling your prescription, be sure to call ahead
prior authorization
Insurance
See Details

Store this drug carefully

  • Store sildenafil tablets at room temperature between 59°F and 86°F (15°C and 30°C).
  • Before mixing, store sildenafil solution at room temperature between 59°F and 86°F (15°C and 30°C).
  • Store the mixed suspension in the refrigerator at a temperature between 36°F and 46°F (2°C and 8°C). Don’t freeze it. 
  • The mixed suspension is good for 60 days. If you have any medication left after this time, throw it away.
  • Keep sildenafil tablets and suspension away from light.
  • Don’t store sildenafil tablets in moist or damp areas, such as bathrooms.

A prescription for this medication is refillable

You should not need a new prescription for this medication to be refilled. Your doctor will write the number of refills authorized on your prescription.

Travel

When traveling with your medication:

  • Always carry your medication with you. When flying, never put it into a checked bag. Keep it in your carry-on bag.
  • Don’t worry about airport x-ray machines. They can’t hurt your medication.
  • You may need to show airport staff the pharmacy label for your medication. Always carry the original prescription-labeled box with you.
  • Don’t put this medication in your car’s glove compartment or leave it in the car. Be sure to avoid doing this when the weather is very hot or very cold.

Clinical monitoring

Your doctor may monitor your blood pressure and pulse regularly.

Insurance

Many insurance companies require a prior authorization for this drug. This means your doctor may need to get approval from your insurance company before your insurance company will pay for the prescription.

Are there any alternatives?

There are other drugs available to treat your condition. Some may be better suited for you than others. Talk to your doctor about other drug options that may work for you.

SECTION 5 of 5

How Much Does sildenafil Cost?

Oral tablet

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Lowest price for sildenafil

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These prices represent the lowest priced national pharmacies for sildenafil on GoodRx. They may be lower than your insurance.

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Content developed in collaboration with University of Illinois-Chicago, Drug Information Group

Medically reviewed by Creighton University, Center for Drug Information and Evidence-Based Practice on November 11, 2015

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.
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