Viagra (sildenafil)

What is Viagra?

Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re unable to have or maintain an erection. Viagra is approved for this use in males ages 18 years and older.

Viagra contains the drug sildenafil. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. (A class of drugs is a group of medications that act in a similar way.) Viagra works by increasing blood flow to your penis, which helps you have and keep an erection. But this drug only works if you’re sexually aroused.

Viagra comes as tablets that are taken by mouth. In most cases, it should be taken about an hour before sexual activity, but it can be taken 30 minutes to 4 hours beforehand. Viagra is available in three strengths: 25 mg, 50 mg, and 100 mg.
Does Viagra work to treat ED?

Yes, it does. In several clinical studies, Viagra was effective in treating ED. In these studies, men who used the drug had an improved ability to have and keep erections that allowed for successful sex.

Across the studies, between 43% and 83% of men who took Viagra had improved erections. (These rates varied depending on the cause of their ED and the dosage of Viagra being used.) In comparison, improved erections occurred in 10% to 24% of men who took a placebo (no active drug).

To learn more about Viagra’s effectiveness, see the “Viagra uses” section below.
Viagra generic

Generic versions of Viagra are available. A generic drug is an exact copy of the active drug in a brand-name medication. The generic is considered to be as safe and effective as the original drug. Generics tend to cost less than brand-name drugs.

Viagra contains the active drug sildenafil.
Viagra side effects

Viagra can cause mild or serious side effects. The following lists contain some of the key side effects that may occur while taking Viagra. These lists don’t include all possible side effects.

For more information on the possible side effects of Viagra, talk with your doctor or pharmacist. They can give you tips on how to deal with any side effects that may be bothersome.

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

Mild side effects of Viagra can include:*

headache
flushing
indigestion
mild and temporary vision changes, such as a blue tinge in your vision, blurred vision, and sensitivity to light
nasal congestion (stuffy nose)
back pain
muscle pain
nausea
dizziness
rash

Most of these side effects may go away within a few days or a couple of weeks. But if they become more severe or don’t go away, talk with your doctor or pharmacist.

* This is a partial list of mild side effects from Viagra. To learn about other mild side effects, talk with your doctor or pharmacist, or view the drug’s patient information.
Serious side effects

Serious side effects from Viagra aren’t common, but they can occur. 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:

Non-arteritic anterior ischemic optic neuropathy (NAION), which is an eye condition that causes damage to your optic nerve. Symptoms can include:
sudden decrease in vision in one or both of your eyes
sudden loss of vision in one or both of your eyes
Sudden decrease or loss of hearing. This condition may also involve other symptoms, such as:
tinnitus (ringing or buzzing in your ears)
dizziness

Other serious side effects, which are explained in more detail below in “Side effect details,” include:

allergic reaction
priapism (long-lasting and sometimes painful erection)
low blood pressure, if Viagra is taken with certain other medications
cardiovascular problems, such as heart attack, irregular heartbeat, or stroke, all of which occur mainly in people with heart disease

Side effect details

You may wonder how often certain side effects occur with this drug. Here’s some detail on several of the side effects this drug may cause.
Allergic reaction

As with most drugs, some people can have an allergic reaction after taking Viagra. In clinical studies, less than 2% of people who took Viagra had an allergic reaction. It’s not known how often allergic reactions occurred in people who took a placebo (no active drug).

Symptoms of a mild allergic reaction can include:

skin rash
itchiness
flushing (warmth and redness in your skin)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:

swelling under your skin, typically in your eyelids, lips, hands, or feet
swelling of your tongue, mouth, or throat
trouble breathing

Call your doctor right away if you have a severe allergic reaction to Viagra. But call 911 if your symptoms feel life threatening or if you think you’re having a medical emergency.
Priapism

Rarely, Viagra can cause priapism, which is a long-lasting and sometimes painful erection. But it’s not known how often priapism occurs in men who take Viagra.

Priapism is a medical emergency that needs to be treated right away. If it’s not treated, the condition can damage the tissues in your penis and cause irreversible erectile dysfunction (ED).

If you have an erection that lasts longer than 4 hours, go to the nearest emergency room or call 911.