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

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

Sildenafil is a popular treatment for ED. Those with this condition 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, and 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 cannot get sildenafil without a valid prescription from a doctor in the United States.

Sildenafil comes in tablet form and is available in strengths of 25, 50, and 100 milligrams (mg). It also comes in 20 mg doses as the generic form of Revatio, but it does not have Food and Drug Administration (FDA) approval for treating ED.

People generally take a 50 mg sildenafil tablet approximately 1 hour before sex. Regardless of the dose, a person needs to take sildenafil exactly as a doctor recommends and not more than once daily.

Sildenafil is fast-acting, and its effects typically last about 1 hour. However, the drug 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 belongs to 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.

Though sildenafil does not cure ED, 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 try taking sildenafil if they first discuss it with a healthcare professional to ensure it is suitable. If appropriate, a doctor will provide a prescription.

The United Kingdom’s National Health Service (NHS) 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, most children over 1 year and adults can take sildenafil for this purpose.

ED may sometimes signify 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.

People cannot take sildenafil if they are already taking nitrate medication that lowers their blood pressure. 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.

Other people who cannot take sildenafil include those with:

  • hypersensitivity to any ingredient in the drug
  • pulmonary veno-occlusion
  • left ventricular outflow obstruction
  • pulmonary arterial hypertension with sickle cell anemia
  • multiple system atrophy

Sildenafil can negatively interact with some medications, hindering their effectiveness or causing side effects.

Some types of medication a person should not take alongside sildenafil include:

  • Nitrates: Combing nitrates and sildenafil can cause very low blood pressure levels. This includes street drugs containing nitrates known as poppers.
  • Blood pressure medications: Taking blood pressure medications and sildenafil together can significantly reduce blood pressure levels.
  • Other PDE5 inhibitors: Taking sildenafil with another PDE5 inhibitor can increase the risk of side effects.

If a person is taking or plans to take any other medications, they need to inform their doctor before taking sildenafil. They should also mention to a doctor any vitamins, supplements, or herbal products that they take or plan to take before taking this medication.

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 using sildenafil who experiences these side effects should seek immediate medical attention.

Dietary interactions

A person needs to avoid consuming large amounts of grapefruit with 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 side effects, including:

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

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 indicator of a sildenafil overdose is vision changes, including impaired blue and green color distinction and blurred vision.

There are no antidotes available for a sildenafil overdose. If a person takes an overdose of this drug, they need to seek immediate medical attention 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. Counterfeit ED medication is common, so MNT only features brands that provide genuine sildenafil.
  • 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.

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The table below compares the telehealth companies offering sildenafil and Viagra.

PriceAccepts insuranceForms offeredConsultation cost
Roman$4–$10 no• sildenafil
• Viagra
Hims$4–$10no• sildenafil
• Viagra
Optumdependant on pharmacynono information$25

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

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

Alternative PDE5 inhibitors include:

  • Avanafil (Stendra): This option increases blood flow to the penis and is available as regular and orally-dissolving tablets. A 2022 study that included 220 participants and lasted 12 weeks found that avanafil is slightly more effective than sildenafil and may work more quickly.
  • Tadalafil (Cialis): This drug helps people get erections by increasing blood flow to the penis. The NHS states that tadalafil can be effective at helping people achieve erections for up to 36 hours.
  • Vardenafil (Levitra): This works by increasing blood flow to the penis. It dissolves in the mouth, so a person does not need to take it with water. A meta-review of 14 studies found that vardenafil significantly improved erectile function in comparison to a placebo.

Other treatment options include:

  • ED pumps: This type of device helps someone get an erection by creating a vacuum around and drawing blood into the penis. A person can then maintain the erection for up to 30 minutes by slipping an elastic ring around the base of their penis. Learn about the best penis pumps.
  • Penile implants: This approach is generally a recommendation for older individuals who did not acquire effective results from treating ED with medication. It involves a surgical procedure to insert a prosthetic device into the penis. The device, which can be either bendable or inflatable, stiffens the penis enough for sex. According to one study, between 83.2 and 85.4% of individuals and their partners were satisfied with the effectiveness of penile implants 1 year after surgery.
  • Penile injections: This technique involves a person injecting Alprostadil, which some individuals mix with other medication, into the side of their penis. It is reportedly effective in helping people develop an erection and is usually well tolerable. Individuals can inject themselves but need to learn how to do it in a doctor’s office first.
  • Prescription testosterone: Testosterone therapy treatment can improve ED either by itself or in combination with medications such as Viagra. However, a person must have both a low sex drive and low blood levels of testosterone for this treatment to be effective. According to the Urology Care Foundation, such cases are rare.

People may also wish to consider making lifestyle adjustments to help manage ED symptoms.

Counseling may benefit people with ED and related health issues, such as cardiovascular problems and obesity. This counseling will cover lifestyle changes a person can make to improve their overall health and potentially their erectile function. These may include:

  • quitting smoking, if they smoke
  • limiting alcohol intake, if they drink
  • increasing physical activity

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 also help.

Sildenafil can help someone have and maintain an erection with sexual stimulation.

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

Sildenafil is the active ingredient in Viagra. Both sildenafil and Viagra come in doses of 25, 50, and 100 mg. There should be no difference between taking sildenafil or Viagra.

Yes, it is okay to take 100 mg of sildenafil, so long as that is the dose a healthcare professional has prescribed. This is the maximum dose available.

Sildenafil is the generic version of the brand name drug Viagra. It is an effective erectile dysfunction (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 need to discuss their treatment options with a doctor before taking any medications.