What is Viagra: Uses, Warnings & Interactions

Medically reviewed by Karen BergerPharm.D.
Licensed Pharmacist
Updated Jan 19, 2024  •  Published Dec 30, 2020
Fact Checked

Viagra overview

BRAND NAMES:

  • Viagra

Generic Names:

Uses:

  • Used in combination with sexual stimulation for erectile dysfunction. 

  • A generic form of sildenafil (marketed under the brand name Revatio) is used to treat pulmonary arterial hypertension (high blood pressure in the lungs).

Therapeutic Classes:

  • Phosphodiesterase-5 (PDE 5) inhibitor

Forms:

  • Tablet

How it’s taken:

  • By mouth

What is Viagra used for?

Viagra is a medication used to treat erectile dysfunction. Viagra belongs to a group of medications called PDE5 inhibitors.

Viagra is the trade name of the drug sildenafil. Viagra was discovered by the drug company Pfizer and was approved by the United States Food and Drug Administration (FDA) in 1998. For erectile dysfunction, Viagra is commonly prescribed.

  • Viagra contains the active ingredient sildenafil. It is used for erectile dysfunction, in combination with sexual stimulation.

What form(s) does Viagra come in

  • Tablet

    • 25 mg

    • 50 mg

    • 100 mg

What are common Viagra doses?

  • The usual recommended dose is 50 mg taken once, as needed, about one hour prior to sexual activity. 

  • However, Viagra can be taken anywhere from 4 hours prior to sexual activity up until 30 minutes prior to sexual activity.

  • Do not exceed one tablet daily, regardless of the dosage. 

  • You can take Viagra with or without food.

  • Your healthcare provider may change the dose if required—for example, to a lower dose of 25 mg, or a higher dose of 100 mg.

Common Viagra prescriptions

  • Viagra
    1 tablets blister

  • Viagra
    10 tablets bottle

  • Viagra
    100 tablets bottle

  • Viagra
    12 tablets bottle

  • Viagra
    18 tablets bottle

  • Viagra
    2 tablets bottle

  • Viagra
    30 tablets bottle

  • Viagra
    3000 tablets bottle

  • Viagra
    4 tablets bottle

  • Viagra
    6 tablets bottle

  • Viagra
    720 tablets bottle

  • Viagra
    9000 tablets bottle

  • Viagra
    30 tablets box

  • Viagra
    100mg tablet

  • Viagra
    25mg tablet

  • Viagra
    50mg tablet

How to take Viagra

  • Before taking Viagra, carefully read the prescription label and patient information leaflet. Ask your healthcare provider or pharmacist if you have any questions.

  • Your doctor will tell you how much medicine to use. Do not use more than directed.

  • For erectile dysfunction: Take this medicine about 1 hour before you have sex. Do not take it more than once a day. Always allow at least 24 hours between doses. Viagra only works in combination with sexual stimulation. You will not have an erection just by taking a tablet.

  • Store the medicine at room temperature, away from heat, moisture, and direct light. Keep out of reach and out of sight of children and pets. Keep the bottle tightly closed when not in use. Do not share your medication with anyone.

  • While taking Viagra, avoid alcohol and grapefruit juice. Also, do not take other medications that treat ED.

What to do if you miss a dose of Viagra

  • Viagra is only taken once as needed. There is no dosing schedule.

Viagra contraindications

  • This medicine is not right for everyone. Do not use it if you have had an allergic reaction to sildenafil, Viagra, Revatio, or any ingredients in the medication.

  • Do not take Viagra if you are taking a nitrate drug such as nitroglycerin tablets or isosorbide mononitrate.

  • People who are taking a guanylate cyclase stimulator, such as Adempas (riociguat) or Verquvo (vericiguat), should not take Viagra.

Viagra warnings

  • Tell your doctor if you are pregnant or breastfeeding, or if you have kidney problems, liver disease, bleeding conditions, eye or vision problems, a history of medical conditions of the penis, any type of blood pressure or heart problems, stomach bleeding, or blood diseases like sickle cell anemia or leukemia. Also, tell your doctor if you smoke.

  • Tell any doctor who treats you that you take sildenafil.

  • This medicine may cause the following problems:

    • Low blood pressure (especially if taken with other medicines that lower blood pressure) and fainting

    • Heart problems: if during sexual activity, you become dizzy or nauseous, or have pain or numbness in the chest, arms, neck, or jaw, stop immediately and get emergency medical help.

    • Painful or prolonged erection (seek emergency medical help if an erection lasts more than 4 hours)

    • Sudden vision loss or hearing problems, which require emergency medical care

  • Keep all medicine out of the reach of children. Never share your medicine with anyone.

Viagra interactions

  • Before taking Viagra, tell your healthcare provider about all the medications you take, including prescription and nonprescription drugs, vitamins, and dietary supplements.

  • Avoid alcohol and grapefruit juice while taking Viagra.

  • Do not use this medicine if you also use Adempas (riociguat), Verquvo (vericiguat), or nitrate medicine. 

  • While taking Viagra, do not take other medicines that contain sildenafil—or similar ED medicines, such as Cialis (tadalafil) or Levitra (vardenafil).

  • Some medicines can affect how sildenafil works. Tell your doctor if you are using any of the following: amlodipine, atazanavir, bosentan, cimetidine, erythromycin, itraconazole, ketoconazole, rifampin, ritonavir, saquinavir, or medicine for prostate problems or high blood pressure (including alfuzosin, doxazosin, prazosin, silodosin, tamsulosin, terazosin).

Viagra side effects

If you have symptoms of an allergic reaction, such as hives, trouble breathing, or swelling of the face, lips, tongue, or throat, get emergency medical help. 

You should also get emergency medical help if you have:

  • Symptoms of a heart attack, such as chest pain, pain that spreads to the jaw or shoulder, nausea, or sweating 

  • Sudden vision or hearing loss

  • A painful erection

  • An erection that lasts longer than 4 hours (priapism)

Serious side effects

  • Sudden loss of vision; blurry vision

  • Sudden decrease or loss of hearing; ringing in the ears

  • Allergic reaction

  • Heart attack

  • Stroke 

  • Fast, slow, pounding, or uneven heartbeat

  • Dizziness, lightheadedness, fainting

  • Painful erection or an erection that lasts longer than 4 hours

Less serious side effects

Some common side effects of Viagra include:

  • Stomach problems: heartburn, nausea, diarrhea

  • Seeing a blue tinge on objects or having difficulty differentiating blue and green

  • Flushing (feeling warm)

  • Headache

  • Stuffy or runny nose

  • Nosebleeds

  • Muscle, back, arm, or leg pain

Sources:

Medically reviewed by Karen BergerPharm.D.
Licensed Pharmacist

After receiving her doctorate from the University of Pittsburgh School of Pharmacy, Karen Berger, Pharm.D., has worked in both chain and independent community pharmacies. She currently works at an independent pharmacy in New Jersey. Dr. Berger enjoys helping patients understand medical conditions and medications—both in person as a pharmacist, and online as a medical writer and reviewer.

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