Sildenafil (Oral Tablet): Side Effects, Dosage, Uses, and Review

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

Sildenafil oral tablet is available as the brand-name drugs Viagra and Revatio. It’s also available as a generic drug. Generic drugs usually cost less than the brand-name version. In some cases, they may not be available in every strength or form as the brand-name drug.

Why it’s used

Sildenafil oral tablet is used to treat ED and PAH. Generic oral tablets are available for both conditions, but the brand-name drugs each treat only one of the conditions.

  • Viagra: This drug is used to treat ED. With ED, you’re unable to get or maintain an erection.
  • Revatio: This drug is used to treat PAH. With PAH, the blood pressure in your lungs is too high. Your heart has to work very hard to pump blood into your lungs.

How it works

Sildenafil 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.

Sildenafil works in different ways, depending on the condition it’s being used to treat.

  • For ED: Sildenafil works by increasing blood flow to the penis. This helps you get or maintain an erection. Sildenafil only works for ED if you’re sexually aroused.
  • For PAH: Sildenafil works by relaxing the muscles and opening up the blood vessels in your lungs. This decreases the blood pressure in your lungs. Sildenafil slows down the progression of your illness. It also makes you more able to exercise.

How sildenafil is used

How long before sex should I use sildenafil?

Sildenafil can be used as early as 4 hours before sex and as late as 30 minutes before sex. However, it is recommended to use this drug within an hour before sex.

How often should I take sildenafil?

Sildenafil should not be taken for ED more than once in a 24-hour period. But if you have certain medical conditions or are taking other drugs, your doctor may recommend that you take this drug less often than once a day.

Should I take sildenafil with food?

Sildenafil can be taken with food or without food. It is important to note that certain foods, particularly foods high in fat, can cause the drug to work more slowly than normal.

Sildenafil side effects

Sildenafil oral tablet doesn’t cause drowsiness, but it can cause other side effects, including:

  • 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
  • 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 with your doctor or pharmacist.

Serious side effects

Call your doctor right away if you have serious side effects. Call 911 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
    • sudden vision loss in one or both eyes
    • sudden hearing loss
    • tinnitus (ringing in your ears)
    • dizziness
    • chest pain
    • shortness of breath
    • dizziness
    • trouble speaking
    • confusion
    • nausea or vomiting
    • feeling lightheaded
    • Priapism warning: This drug can cause priapism, which is an erection that won’t go away. If you have an erection that lasts more than 4 hours, call 911 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 warning: This drug can cause sudden vision loss in one or both eyes. This can be a sign of a serious eye problem. If this occurs, stop taking sildenafil and call your doctor right away.
    • Sudden hearing loss warning: This drug can cause hearing loss, tinnitus (ringing in your ears), or dizziness. If you have sudden hearing loss with or without tinnitus or dizziness, stop taking sildenafil and call your doctor right away.
    • Use in children warning: Children generally should not take sildenafil; however, there are instances where the drug is considered the best treatment option. Talk with your child’s doctor to better understand the benefits and risks associated with this treatment option.

    Sildenafil oral tablet 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 with your doctor or pharmacist.

    Examples of drugs that can cause interactions with sildenafil are listed below.

    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.
      • Taking these drugs with sildenafil can cause your blood pressure to drop suddenly to an unsafe level.

      Interactions that increase your risk for side effects

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

      • 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.
        • Increased side effects can include low blood pressure, dizziness, or vision problems. They can also include erections that last longer than normal.
        • 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 for 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.
          • Increased side effects can include blood pressure that’s too low.
          • 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.

          This drug comes with several warnings.

          Allergy warning

          Sildenafil can cause a severe allergic reaction. Symptoms can include:

          • trouble breathing
          • swelling of your throat or tongue

          If you develop these symptoms, call 911 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).

          Alcohol interaction warning

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

          Warnings for people with certain health conditions

          For 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.

          For people with pulmonary veno-occlusive disease (PVOD): Taking this drug may worsen your heart function. You should not take this drug.

          For 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 for NAION and vision changes with this drug.

          For 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 for having an erection that lasts more than 4 hours.

          For people with a history of stomach ulcers or bleeding: This drug raises your risk for 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.

          For 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.

          Warnings for other groups

          For pregnant women: Research in animals has not shown a risk to the fetus when the mother takes the drug. However, there aren’t enough studies done in humans using the drug for PAH to show if the drug poses a risk to the fetus.

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

          Viagra or generic sildenafil for ED should not be used in women.

          For women who are breastfeeding: When used for PAH, sildenafil may pass into breast milk and may cause side effects in a child who is breastfed. Talk with your doctor if you breastfeed your child. You may need to decide whether to stop breastfeeding or stop taking this medication.

          Viagra or generic sildenafil for ED should not be used in women.

          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, a higher amount of a drug stays in your body for a longer time. This raises your risk for side effects.

          For children: This drug isn’t recommended in children younger than 18 years. In one study, children with PAH who took this drug had an increased chance for death.