Viagra (sildenafil)

Medically Reviewed By Tanya Kertsman, PharmD

About Viagra

Viagra is a brand-name prescription medication. It’s approved by the Food and Drug Administration (FDA) to treat erectile dysfunction (ED) in adult males.*

With ED, you have trouble getting and keeping an erection that’s firm enough to have sex.

For details about this condition and how the drug treats it, see the “Viagra: Uses” section below.

* Sex and gender exist on spectrums. In this article, use of the term “male” refers to sex assigned at birth.

Key points

The following table provides key facts about Viagra.

Active drug sildenafil
Drug class phosphodiesterase-5 (PDE5) inhibitor
Form oral tablet

Finding a healthcare professional

If you’re interested in taking this drug, search here to find a doctor who might prescribe it.

Viagra: Generic

Viagra is a brand-name medication. It contains the active drug sildenafil, which also comes in a generic form. A generic is an identical copy of the active drug found in a brand-name medication.

The Food and Drug Administration (FDA) ensures that generic drugs are as safe and effective as their original drug. Generics tend to be less expensive than brand-name drugs.

If you’d like to know about using the generic version of Viagra, ask your doctor or pharmacist. They can tell you if the generic medication comes in forms and strengths recommended for your condition.

Viagra: Use in women

You may wonder if Viagra can be used to treat sexual problems in females as it is in males. Below are answers to some frequently asked questions on this subject.

If you would like more information about possible uses of Viagra in females, talk with your doctor.

Note: Sex and gender exist on spectrums. In this article, use of the terms “male” and “female” refers to sex assigned at birth.

Can women take Viagra?

Doctors are unlikely to prescribe Viagra for females. The drug is only approved by the Food and Drug Administration (FDA) to treat erectile dysfunction (ED) in males. Also, there’s not enough evidence to show that it can help with sexual problems in females.

What happens if a woman takes Viagra?

In males, Viagra treats ED by increasing blood flow to the penis by blocking an enzyme called PDE5. (For details, see “Viagra: How it works” below.) The vagina and clitoris also contain PDE5. So, if a female takes Viagra, the drug may increase blood flow to these areas.

However, female genitals contain less PDE5 than male genitals, so Viagra may have less of an effect in females. As well, female sexual function relies heavily on desire and arousal. Viagra isn’t likely to improve problems with desire and arousal.

One review of studies found conflicting results on how Viagra may affect females with sexual arousal disorder. (Sexual arousal disorder is trouble becoming or staying aroused with or without changes in sexual desire.) For example, in one study, postmenopausal females found that Viagra improved vaginal lubrication, arousal, and orgasm. However, in another study, females found that Viagra had no significant positive effects.

Viagra: Alternatives

Doctors may prescribe drugs other than Viagra for erectile dysfunction (ED). Certain drugs may work better for you than others.

Viagra is used to treat ED. Here’s a summary of other drugs that doctors sometimes prescribe for this condition. Read below for information about some specific alternative drugs.

Viagra vs. Cialis and other drugs

To learn more about some alternatives of Viagra, view the following articles:

If you would like additional information about alternatives to Viagra, ask your doctor. They can tell you about other medications that could be prescribed for your condition.

* The brand-name drug Levitra is no longer available. However, its generic drug, vardenafil, is available. If you’d like to know more about taking the generic form of Levitra, talk with your doctor or pharmacist.

Viagra: Side effects

As with most drugs, it’s possible to have side effects with Viagra. These can include some mild side effects, but also some serious ones.

To learn more about Viagra’s side effects, talk with your doctor or pharmacist. They may also provide information about managing certain side effects of this drug.

Note: The Food and Drug Administration (FDA) tracks side effects of drugs it has approved. If you would like to notify the FDA about a side effect you’ve had with Viagra, you can do so through MedWatch.

Mild and serious side effects

Mild and serious side effects of Viagra are listed in the table below. This table does not include all of Viagra’s possible side effects.

Mild side effects* Serious side effects
flushing priapism, which is a long-lasting, painful erection
headache • cardiovascular problems, such as irregular heartbeat, heart attack, or stroke
• indigestion low blood pressure, if Viagra is taken with certain other drugs
muscle or back pain • sudden hearing problems
• temporary vision changes, such as blue-tinted vision, blurry vision, or increased sensitivity to light • sudden loss of vision occurring in one or both eyes, which could be a symptom of non-arteritic anterior ischemic optic neuropathy (NAION), an eye condition that can damage your optic nerve
stuffy nose allergic reaction
nausea  
dizziness  
rash  

* This is not a complete list of Viagra’s mild side effects. To learn about other mild side effects of this drug, ask your doctor or pharmacist. Or you can view the drug’s prescribing information.
† For more information about allergic reaction, see below.

Most times, mild side effects of a drug go away within a few days or a couple of weeks. Talk with your doctor or pharmacist if any side effects become severe or don’t go away.

Serious side effects from Viagra aren’t common, but they are possible. If you have serious side effects, call your doctor right away. However, if you’re having a medical emergency or your symptoms feel life threatening, call 911 or a local emergency number.

Allergic reaction

As with most drugs, some people can have an allergic reaction after taking Viagra. A more severe allergic reaction is rare but possible.

Possible symptoms of mild and serious allergic reactions are listed in the table below.

Mild allergic reaction symptoms Serious allergic reaction symptoms
flushing • swelling under your skin, possibly in your hands, feet, lips, or eyelids
rash • swelling in your throat or mouth
• itching trouble breathing

If you have an allergic reaction to Viagra, call your doctor right away. This is important to do because the reaction could become severe.

However, if you’re having a medical emergency or your symptoms feel life threatening, call 911 or a local emergency number.

Viagra: How it works

Viagra treats erectile dysfunction (ED) by helping you get and keep an erection when you’re sexually aroused. For details about this condition, see the “Viagra: Uses” section below.

What happens with an erection?

When you’re sexually aroused, your brain sends signals to your penis. The signals cause a chemical called cyclic GMP to be released in your penis.

Cyclic GMP widens the blood vessels in your penis. It also relaxes the corpus cavernosum (the erectile tissue in your penis), allowing it to fill with blood. The increased blood in your penis causes it to become hard and erect.

Your erection goes away when an enzyme called phosphodiesterase-5 (PDE5) breaks down the cyclic GMP. (An enzyme is a protein that helps chemical reactions happen.)

What happens with ED?

With ED, blood flow to your penis doesn’t occur like usual. Or there may be problems with the signals your brain sends to your penis. These difficulties lead to trouble getting and keeping an erection.

What does Viagra do?

Viagra is a type of drug called a PDE5 inhibitor. It stops PDE5 from breaking down the cyclic GMP in your penis, which keeps the cyclic GMP active for longer. This improves the blood flow in your penis and allows you to get and keep an erection.

How long does Viagra take to start working?

Viagra usually starts working within 30 minutes to 2 hours. Note that Viagra only works to help you get and keep an erection if you’re sexually aroused. Causes of arousal may include thoughts or touch.

How long does Viagra stay in your system?

Viagra works for about 4 hours after you take a dose. It takes about 20 hours for the drug to be fully removed from your system.

Viagra: Dosage

Below, you’ll find dosages that are commonly recommended for Viagra. However, you should take the dosage your doctor prescribes for you. They’ll recommend the dosage that’s best for your needs.

Most often, doctors start by prescribing a low dosage of Viagra. Then, they’ll change the dosage over time to an amount that’s right for the condition being treated. Doctors typically prescribe the smallest dosage that gives the desired outcome.

The dosage of Viagra that your doctor prescribes will depend on factors such as:

  • your age
  • any health conditions you have
  • other medications you take

Viagra’s forms and strengths

Viagra is available as follows.

  • Form: oral tablets
  • Strength: 25 milligrams (mg), 50 mg, and 100 mg

Viagra’s recommended dosage

The recommended dosage for Viagra is described below.

Adult dosage

The usual recommended dosage for Viagra in adults is as follows.

  • Dose: 50 mg, taken about 1 hour before sexual activity or within 30 minutes to 4 hours before having sex
  • Frequency: when needed, but no more than once per 24 hours

Doctors may prescribe a dose of 25 mg if you take certain medications or have other factors affecting your health. These may include liver problems, kidney problems, or older age. However, a change in dosage by weight isn’t needed.

Dosage considerations

Below are some things to consider about Viagra’s dosage.

  • Dose adjustments. If a 50-mg dose doesn’t work for you, your doctor may increase your dose to a maximum of 100 mg. If you have bothersome side effects, your doctor may decrease your dose.
  • Length of treatment. Doctors may prescribe Viagra for as long as you need it if it’s safe and effective for you.

Viagra: Questions you may have

Here are some common questions about Viagra and brief answers to them. If you’d like to know more about these topics, ask your doctor.

Will Viagra make my penis bigger?

No, Viagra will not make the penis bigger.

Viagra helps you get and keep an erection. An erection happens when an extra supply of blood enters the penis. This causes it to become hard and erect, which can make your penis appear bigger. However, it won’t permanently increase the size of your penis.

If you have questions about what to expect with Viagra, talk with your doctor.

Is Viagra considered safe to take?

Yes, Viagra is typically safe to take. However, Viagra may not be considered safe if you have certain medical conditions, such as heart disease, or if you take certain medications, such as nitrates. To find out what conditions and medications could make Viagra unsafe to take, see “Viagra: Precautions” and “Viagra: Interactions” below.

Like all drugs, Viagra has some serious side effects. To learn more about Viagra’s side effects, see “Viagra: Side effects” above.

If you have concerns about taking Viagra, talk with your doctor. Be sure to tell them about all of your other medical conditions and all of the medications you are currently taking.

Do doctors prescribe 200-mg Viagra doses?

No, they don’t. The maximum dose of Viagra prescribed by doctors is 100 milligrams (mg). For more information, see “Viagra: Dosages” above.

If you have questions about what dose of Viagra may be right for you, talk with your doctor.

Viagra: How to take

Your doctor will recommend how you should take Viagra. It’s important that you take the drug exactly as your doctor instructs.

Questions about taking Viagra

Here’s a list of common questions related to taking Viagra.

  • When should I take Viagra? You should take Viagra between 30 minutes and 4 hours before sexual activity. Most people take it about 1 hour before having sex.
  • How often can I take Viagra? Viagra can be taken as needed. However, you should not take Viagra more than once per day.
  • Do I need to take Viagra with food? You can take Viagra either with or without food. However, if you take it with food, especially a high fat meal, it may take about an hour longer to start working.
  • Can Viagra be chewed, split, or crushed? It’s not known for sure if it’s safe to chew, split, or crush Viagra tablets. Ask your doctor or pharmacist about this if you’re unable to take the tablets whole.
  • Is there a best time of day to take Viagra? No, there’s no best time of day to take Viagra.

Viagra: Consuming alcohol during treatment

There is no known interaction between Viagra and alcohol. However, consuming alcohol with Viagra may increase some of its side effects, such as headache, dizziness, nausea, and flushing.

As well, consuming alcohol can sometimes cause trouble having an erection. And Viagra is used to treat erectile dysfunction (ED). So, Viagra may not work as well as usual if you drink alcohol with it.

If you drink alcohol, ask your doctor how much is safe, if any, to consume with Viagra.

Viagra: Interactions

Viagra may interact with certain other medications.

Different interactions can cause different effects. Some interactions can interfere with a drug’s effectiveness. Others can increase a drug’s side effects or cause them to be severe.

If any of the interactions listed below might pertain to you, talk with your doctor. They can tell you what you need to do to avoid the interaction.

  • Viagra and nitrates. The manufacturer of Viagra advises that these drugs should not be taken together. The combination could cause a drop in blood pressure that leads to a heart attack or stroke. Due to this interaction, doctors typically will not prescribe Viagra with nitrates. Examples include:
    • alkyl nitrate
    • amyl nitrate
    • butyl nitrate
    • glyceryl trinitrate
    • isosorbide mononitrate (Monoket)
    • isosorbide dinitrate (Dilatrate SR, Isordil)
    • nitroglycerin (Nitromist, Nitro-Dur, Nitrolingual Pumpspray, GoNitro, others)
  • Viagra and certain drugs for pulmonary arterial hypertension (PAH). The manufacturer of Viagra advises that certain drugs for PAH should not be taken with Viagra. Due to this interaction, doctors typically will not prescribe Viagra with these drugs. Examples include:
    • riociguat (Adempas)
    • sildenafil (Revatio)
    • tadalafil (Adcirca)
  • Viagra and other erectile dysfunction (ED) medications. Because Viagra may interact with other medications for ED, doctors typically will not prescribe Viagra with these drugs. Examples include:
    • alprostadil (Muse, Caverject, Caverject Impulse, Edex)
    • avanafil (Stendra)
    • tadalafil (Cialis)
    • vardenafil (Staxyn)
  • Viagra and alpha-blockers. Because Viagra may interact with alpha-blockers, your doctor may recommend that you don’t take it with these drugs. Or they may prescribe a dose of Viagra that’s lower than usual. Examples include:
    • alfuzosin (Uroxatral)
    • doxazosin (Cardura)
    • silodosin (Rapaflo)
    • tamsulosin (Flomax)
    • terazosin (Hytrin)
  • Viagra and blood pressure medications. Because Viagra may interact with blood pressure medications, your doctor may recommend that you don’t take it with these drugs. Or they may prescribe a dose of Viagra that’s lower than usual. Examples include:
  • Viagra and certain other medications. Because Viagra may interact with certain other medications, your doctor may recommend that you don’t take it with these drugs. Or they may prescribe a dose of Viagra that’s lower than usual. Examples include:
    • certain antibiotics, such as erythromycin (Eryc, Ery-tab) and clarithromycin
    • certain antifungals, such as ketoconazole (Nizoral) and itraconazole (Sporanox)
    • certain HIV drugs, such as ritonavir (Norvir) and nelfinavir (Viracept)

For information about drug-condition interactions, see the “Viagra: Precautions” section below.

Viagra: Uses

Prescription drugs, such as Viagra, are approved by the Food and Drug Administration (FDA) to treat certain conditions.

Using Viagra for erectile dysfunction

Viagra is FDA-approved to treat erectile dysfunction (ED) in males* ages 18 years and older.

With ED, you have trouble getting and keeping an erection that’s firm enough to have sex. ED is a common sexual problem that has many different causes. Some of these are outlined in the table below.

Psychological causes Physical causes
• relationship issues diabetes
• performance anxiety heart disease
• mental health problems, such as depression or anxiety high blood pressure
• stress high cholesterol
  • spinal cord injury
  multiple sclerosis

Viagra is an ED treatment that you take shortly before having sex. It helps improve the blood flow to your penis when you’re sexually aroused, such as through thoughts or touch. This helps you get and keep an erection firm enough to have sex.

* Sex and gender exist on spectrums. In this article, use of the term “male” refers to sex assigned at birth.

Taking Viagra with other drugs

Doctors typically don’t prescribe Viagra with other ED drugs or therapies. Using Viagra with other ED treatments could increase the risk of side effects such as priapism (a prolonged, painful erection).

Using Viagra in children

Viagra is not FDA-approved for people younger than 18 years of age. Doctors typically won’t prescribe Viagra to this age group.

Finding a healthcare professional for Viagra

If you’re interested in taking Viagra, you can find a doctor who may prescribe it by searching here. To prepare for your appointment, you may find it helpful to visit the appointment guide for ED.

Viagra: Expiration, storage, and disposal

Here’s some information about Viagra’s expiration date, as well as how to store and dispose of the drug.

  • Expiration. Your pharmacist will add an expiration date to the label on Viagra’s packaging. This date is usually 1 year from the date the medication was dispensed to you. Expiration dates help ensure that a medication is effective during a period of time. The Food and Drug Administration (FDA) advises that you avoid using expired drugs. If you have an unused medication and it’s past the drug’s expiration date, talk with your pharmacist.
  • Storage. Many factors determine how long a medication remains good to use. These factors include how and where you store the drug. Viagra tablets should be stored at a room temperature of 77°F (25°C). If needed, they can be stored at 59°F to 86°F (15°C to 30°C) at times. Avoid storing them in areas where they could get damp or wet, such as bathrooms. The medication should be in a tightly sealed container.
  • Disposal. It’s important to safely dispose of Viagra if you no longer need to take it and have unused medication. Doing so helps prevent others, including children and pets, from accidentally taking the drug. It also helps avoid causing harm to the environment. Ask your pharmacist for information about disposing of Viagra. Also, check out this page for several tips on safe medication disposal.

Viagra: Cost

Like other medications, prices for Viagra may vary. The drug’s price will depend on factors such as:

Cost considerations for Viagra

Here’s a list of things to consider when looking into the cost of Viagra.

  • Option for a 90-day supply. For some drugs, it’s possible to get a 90-day supply. If this option is approved by your insurance company, it can help lower the cost of the drug. It can also help you avoid frequent trips to your pharmacy. If you’d like to learn more about this option, ask your doctor, pharmacist, or insurance company.
  • Need for prior authorization. Before insurance coverage for Viagra is approved, your insurance company may require prior authorization. In this case, your doctor and insurance company will communicate about your prescription for Viagra. Then, the insurance company will decide if the drug will be covered. To find out if you need prior authorization for Viagra, contact your insurance company.
  • Possible cost assistance options. Financial assistance to help lower the cost of Viagra is available. The Viagra savings card may help reduce the drug’s cost. To learn more and see if you’re eligible for support, visit the manufacturer’s website. Also, check out this article to learn about ways to save on prescription drugs.
  • Use of a mail-order pharmacy. Viagra may be dispensed through mail-order pharmacies. Getting your prescription through a mail-order pharmacy could lower its cost. It can also allow you to get the drug without leaving home. To find out more about this option, check with your doctor, pharmacist, or insurance company.
  • Availability of a generic form. Viagra comes in a generic form called sildenafil. A generic drug is an exact copy of the active drug in a brand-name medication. Generics are typically less expensive than brand-name drugs. If your doctor prescribes Viagra but you want to know about using sildenafil, talk with your doctor about which option might be better for you. Also, check your insurance plan because it might cover just one form or the other.

Viagra: Taking while pregnant

Doctors aren’t sure if it’s safe to use Viagra during pregnancy. It hasn’t been studied in people who are pregnant. Also, note that Viagra isn’t approved by the Food and Drug Administration (FDA) for use in females.

Talk with your doctor if you have any questions about using Viagra during pregnancy.

Note: Sex and gender exist on spectrums. In this article, use of the term “female” refers to sex assigned at birth.

Viagra and birth control needs

It’s not known if it’s safe to use Viagra during pregnancy. Note that Viagra isn’t approved for females. Talk with your doctor about your birth control needs with Viagra if you’re sexually active and you or your partner can become pregnant. Your doctor can recommend if you should use birth control with this medication.

Viagra: Taking while breastfeeding

It’s not known if it’s safe to use Viagra while breastfeeding. The drug may pass into breast milk, but it hasn’t been studied in people who are breastfeeding. Note that Viagra isn’t approved by the Food and Drug Administration (FDA) for use in females.

Talk with your doctor if you have any questions about using Viagra while breastfeeding.

Note: Sex and gender exist on spectrums. In this article, use of the term “female” refers to sex assigned at birth.

Viagra: Precautions

Tell your doctor about your health history before starting treatment with Viagra. Your doctor may not recommend this medication if you have certain factors affecting your health or specific medical conditions. These situations are considered drug-condition interactions.

These factors and conditions include those listed below.

  • Allergic reaction. Your doctor will likely not prescribe Viagra if you’ve had an allergic reaction to it or any of its ingredients. To find out about other treatment options, talk with your doctor.
  • Heart conditions or stroke. Viagra may not be safe for you if you have a heart condition such as angina, heart failure, irregular heartbeat, or aortic stenosis. As well, it may not be safe if you’ve had a stroke, heart attack, or other heart condition in the past. That’s because the combined effect of taking Viagra and having sexual activity could put too much strain on your heart. This could lead to a heart attack or stroke. Talk with your doctor about whether Viagra is right for you.
  • Low or high blood pressure. Viagra may not be safe for you if you have high or low blood pressure. Viagra can lower your blood pressure. If you already have low blood pressure or take medication for high blood pressure, Viagra could cause dizziness or fainting. If you have high blood pressure that’s not managed, taking Viagra and having sex may put too much strain on your heart. Talk with your doctor about whether Viagra is right for you.
  • Physical irregularity of your penis. If you have a condition such as Peyronie’s disease that causes scarring or bending of your penis, Viagra may not be safe for you. That’s because Viagra can sometimes cause priapism (a prolonged, painful erection), which could cause further damage to your penis. Talk with your doctor about whether Viagra is right for you.
  • Certain blood disorders. Viagra can sometimes cause priapism (a prolonged, painful erection). If you have sickle cell anemia, leukemia, or multiple myeloma, you may have an increased risk of this side effect. Talk with your doctor about whether Viagra is right for you.
  • Certain eye conditions. Viagra may not be safe for you if you have retinitis pigmentosa or you’ve ever had non-arteritic anterior ischemic optic neuropathy (NAION). (Retinitis pigmentosa is a hereditary eye disorder that causes loss of vision. NAION is an eye condition that can damage your optic nerve.) Viagra hasn’t been studied in people with NAION. On rare occasions, Viagra may cause NAION. You may have a raised risk of this side effect if you’ve had NAION in the past. Talk with your doctor about whether Viagra is right for you.
  • Kidney or liver problems. If your kidneys or liver aren’t working properly, Viagra could build up in your body. This could raise your risk of Viagra side effects, so your doctor may prescribe a dose of Viagra that’s lower than usual.
  • Bleeding problems. There have been a few reports of bleeding in people taking Viagra.If you have problems with bleeding, talk with your doctor about whether Viagra is safe for you.
  • Peptic ulcer. There have been a few reports of bleeding in people taking Viagra.If you have or have had an active peptic ulcer, you may have a risk of bleeding in your stomach or intestines. Talk with your doctor about whether Viagra is safe for you.
  • Pregnancy. If you’d like more information about using Viagra during pregnancy, view the “Viagra: Taking while pregnant” section above.
  • Breastfeeding. If you’d like more information about using Viagra during breastfeeding, view the “Viagra: Taking while breastfeeding” section above.

To learn more about effects of Viagra that could be harmful, see the “Viagra: Side effects” section above.

Viagra: Overdose

For some drugs, taking more than the recommended dosage may lead to unwanted side effects or overdose. Do not use more Viagra than your doctor advises.

What to do if you take too much Viagra

Call your doctor if you think you’ve taken too much of this drug. Also, you can call the American Association of Poison Control Centers at 800-222-1222 or use its online tool. However, if your symptoms are severe, call 911 or your local emergency number. Or go to the nearest emergency room right away.

Viagra: Questions for your doctor

If you have questions about Viagra, talk with your doctor. They can help advise you on whether Viagra could be a good treatment option for you.

Here’s a list of questions you may want to ask your doctor:

  • Can Viagra interact with my other medications?
  • Is Viagra safe with my heart condition?
  • Can Viagra worsen any of my health conditions?

Your doctor may also tell you about other treatment options for your condition. You may find this article helpful in learning about alternative drugs for erectile dysfunction.

Disclaimer: Healthgrades 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 another 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.

Medical Reviewer: Tanya Kertsman, PharmD
Last Review Date: 2022 May 19
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.