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Sildenafil is a drug for treating erectile dysfunction (ED) and is the active ingredient in Viagra. We cover sildenafil uses, dosage, and more in this article. We also feature the best places to buy sildenafil.

This article takes a closer look at sildenafil, ED, and how the drug works to relieve the condition.

Sildenafil is a popular treatment for ED. People with ED have difficulty getting or maintaining an erection. It is a widespread condition, but many people find it difficult to discuss.

The main ingredient in sildenafil is sildenafil citrate. The inactive ingredients include:

  • microcrystalline cellulose
  • anhydrous dibasic calcium phosphate
  • croscarmellose sodium
  • magnesium stearate
  • hypromellose
  • titanium dioxide
  • lactose
  • triacetin
  • artificial colors

Viagra is just one brand name option containing sildenafil. Other products might use different inactive ingredients.

Another brand name medication containing sildenafil is Revatio. In addition to treating ED, Revatio treats pulmonary hypertension.

A person who wishes to use sildenafil for ED should contact a doctor because the medication is available by prescription only in the United States.

Sildenafil comes in tablet form. Tablets are available in strengths of 25, 50, and 100 milligrams (mg).

People generally take a 50-mg sildenafil tablet approximately 1 hour before sex. Regardless of the dose, a person should not take sildenafil more than once a day.

Sildenafil is fast acting, and its effects typically last about 1 hour. However, sildenafil does not instantaneously produce an erection, and sexual arousal is necessary for the drug to work. Sildenafil also does not affect a person’s sex drive, or libido.

Sildenafil falls into a class of medications called phosphodiesterase type 5 (PDE5) inhibitors. These inhibit phosphodiesterase enzymes, which degrade the molecules that relax the muscle tissue. This allows for increased blood flow, causing an erection.

Sildenafil does not cure ED. However, it can help treat the symptoms of the condition.

People are more likely to experience adverse reactions to the drug if they take more than the recommended amount.

A person with symptoms of ED can take sildenafil if they first discuss it with a healthcare professional to ensure it is the right treatment for them. If appropriate, a doctor will provide a prescription.

The National Health Service (NHS) in the United Kingdom states that most males over the age of 18 can take sildenafil for ED.

People with pulmonary arterial hypertension can also take sildenafil to treat their symptoms. According to the NHS in the United Kingdom, most children over 1 year and adults can take sildenafil for this purpose.

ED may sometimes be a sign of an underlying condition, so sildenafil may help treat some symptoms in individuals with certain health conditions.

Some people with the following conditions may take sildenafil for treating ED:

Learn more about the causes of ED.

Some common side effects of sildenafil include:

More serious side effects can include sudden loss of vision or hearing, and prolonged, painful erections, known as priapism. Anyone experiencing these side effects should seek immediate medical attention.

Dietary interactions

A person should avoid consuming large amounts of grapefruit when taking sildenafil. Consuming grapefruits or grapefruit juice can increase the levels of sildenafil in the body, potentially leading to toxicity.

Combining sildenafil with alcohol can also cause interactions. A 2019 study found that people who take sildenafil and other PDE5 inhibitors alongside alcohol can lead to common sildenafil side effects, including:

  • indigestion
  • skin rash
  • headache
  • facial flushing
  • chest discomfort and palpitations
  • dizziness
  • altered vision
  • nasal congestion

Other warnings

If a person takes nitrate medication that lowers their blood pressure, they cannot take sildenafil. This is because sildenafil can further lower blood pressure and cause serious side effects, such as life threatening hypotension.

Nitrate medication includes nitroglycerin, isosorbide mononitrate, and isosorbide dinitrate.

Sildenafil is also unsuitable for people with heart conditions due to its effect on arteries. The drug stimulates the release of nitric oxide, which causes arteries to widen, lowering blood pressure. Although this is typically safe in a person with a healthy heart, it could be detrimental to those with heart conditions.

It is important to note that sildenafil is not a form of birth control, so it does not prevent pregnancy. It also does not protect against sexually transmitted infections.

What to do

If a person has taken too much sildenafil and has trouble breathing, is unconscious, or has a seizure, they or someone near them should call emergency services at 911 immediately.

Otherwise, a person can call America’s Poison Centers for emergency attention at 1-800-222-1222 or visit the Poison Help website.

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A sign of a sildenafil overdose is an increase in the severity and duration of common side effects. Another sign of a sildenafil overdose is visual changes, including impaired blue and green color discrimination and blurred vision.

There are no antidotes available for a sildenafil overdose. If a person takes an overdose of sildenafil, they should seek supportive care immediately or call poison control.

Medical News Today’s methodology

Medical News Today chooses sildenafil retailers based on the following criteria:

  • Company reputation: MNT brands that have undergone internal vetting of medical and business standards. The brands we choose are reputable and reliable, with transparent business practices and positive reviews on the Better Business Bureau and Trustpilot.
  • Product transparency: MNT selects retailers that clearly state its ingredients, side effects, and the recommended sildenafil dosage.
  • Safety: MNT selects brands that require a doctor’s prescription before customers can order sildenafil. This ensures that a person can safely take sildenafil and that the professional is dispensing it responsibly.
  • Price: MNT selects products that suit a range of budgets, including choosing brands that offer both brand-name and generic sildenafil.

Medical News Today follows a strict product selection and vetting process. Learn more here.

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People can use telehealth companies to buy sildenafil online. They will often need to answer health questions and have an online appointment with a doctor before they can get a prescription for sildenafil. Below, we look at the best places to buy sildenafil online.

Please note that the writer of this article has not tried any of these products. All information presented here is purely research-based.

If a person cannot take sildenafil, wishes to avoid it, or wants to try something else, there are other options to treat ED.

Other PDE5 inhibitors include:

  • avanafil (Stendra)
  • tadalafil (Cialis)
  • vardenafil (Levitra)

Other treatment options include:

  • ED pumps
  • penile implants
  • penile injections
  • prescription testosterone

People may also wish to consider making lifestyle adjustments to help manage the symptoms of ED. These may include:

Mental health symptoms may also contribute to ED. Anxiety and stress about sex, for example, can make it more difficult for a person to get or maintain an erection. Talking with a mental health professional may help.

Below, we answer the most frequently asked questions about sildenafil.

What happens if you take too much sildenafil?

If a person takes too much sildenafil, it can cause a range of side effects, including blurred vision, hearing loss, low blood pressure, and a prolonged and painful erection.

In the event of breathing problems, unconsciousness, and seizures, people should call 911 immediately.

Otherwise, people who have taken too much sildenafil can call America’s Poison Centers for emergency help at 1-800-222-1222 or visit the Poison Help website.

What does sildenafil do to a man?

Sildenafil can help a person get and maintain an erection with sexual stimulation.

How long does it take for sildenafil to hit?

Sildenafil should typically begin working within 30–60 minutes after a person takes it. It can continue working for up to 4 hours.

Is sildenafil stronger than Viagra?

Sildenafil is the active ingredient in Viagra. Both sildenafil and Viagra come in doses of 25, 50, and 100 mg. As such, they will be equally as strong.

How long will sildenafil keep you hard?

Sildenafil is usually effective for around 4 hours. However, this does not mean a person will have an erection for this long. The erection should only occur when a person is aroused. If a person experiences an erection that lasts a long time or is painful, they should seek emergency medical attention.

Sildenafil is the generic version of the brand name drug Viagra. Sildenafil is an effective ED drug available at a fraction of the cost of Viagra.

Sildenafil is just as safe and effective as Viagra. However, as with Viagra, it carries the risk of potential side effects and drug interactions.

People who experience ED should discuss their treatment options with a doctor.