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Sildenafil is a drug for treating erectile dysfunction (ED) and also the active ingredient in the brand name drug Viagra. It can help a person get and maintain an erection.

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. 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 (PH). PH involves high blood pressure in the right side of the heart and the arteries of the lungs.

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

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

Some risk factors for ED include:

  • being older
  • having certain medical conditions
  • having mental health issues
  • having excess body weight
  • smoking
  • taking certain medications

ED may sometimes be a sign of an underlying condition. For this reason, people should contact a doctor if they experience difficulty getting or maintaining an erection.

Some conditions that may cause ED include:

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.

The pills come in strengths of 25 milligrams (mg), 50 mg, and 100 mg. People generally take a 50-mg pill approximately 1 hour before sex. Regardless of the dose, a person should not take sildenafil more than once per day.

The drug is fast-acting, and its effects typically last about 1 hour. It is important to note that sildenafil does not instantaneously produce an erection and that sexual arousal is necessary for the drug to work. Sildenafil also does not affect sex drive.

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

Some common side effects of sildenafil include:

  • headaches
  • flushing
  • gastrointestinal distress
  • nausea
  • muscle aches and pains
  • dizziness
  • rashes

Other warnings

It is possible to take too much sildenafil. If a person overdoses on this medication, they should seek medical help immediately.

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

People with concerns about sildenafil may wish to weigh the benefits and downsides of this treatment with a doctor.


  • widely available
  • noninvasive
  • can help with other medical conditions, such as PH
  • flexible, as a doctor can adjust a person’s dosage as required


  • available only with a valid prescription
  • can interact with other medications, such as those for blood pressure
  • the effects do not last long, typically averaging 1 hour
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A person with symptoms of ED can take sildenafil as long as they first discuss it with a healthcare professional.

Sildenafil can also help those with pulmonary arterial hypertension. It works by relaxing and widening the blood vessels in a person’s lungs, which helps blood flow.

As sildenafil requires a valid prescription, a doctor will prescribe an appropriate dosage for an individual. A person should not take more than the prescribed dosage.

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

Sildenafil is also not suitable for people with heart conditions due to the effect it has 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.

A person should ensure they take the correct dosage of sildenafil. If they take more than a healthcare professional describes, they should seek medical advice immediately.

Sildenafil binds itself to plasma in the blood, and the kidneys do not filter it out of the body as it does with certain other medications.

High doses of sildenafil increase the severity and duration of side effects. People may notice an increase in visual changes.

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, causing the medication to be less effective.

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:

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

How we chose

Medical News Today chooses ED products that meet the following criteria:

  • Company reputation: MNT selects products from brands that have undergone internal vetting of medical and business standards. The brands we choose are reputable and reliable, with positive reviews and transparent business practices.
  • Product transparency: MNT selects products that state ingredients, side effects, and the recommended dosage clearly.
  • Safety: MNT selects brands that require a doctor’s prescription before customers can order Cialis. This ensures that a person can safely take Cialis and that the provider is responsible.
  • Price: MNT selects products that suit a range of budgets, including choosing brands that offer both brand-name and generic Cialis.
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Please note that the writer of this article has not tried any of these products. All information presented here is purely research-based.

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

Best low cost option: Roman

  • Sildenafil: starting from $4 per dose
  • Viagra: $90 per dose
  • Cialis (tadalafil): starting from $20 per dose

Roman offers online support for people with ED and other health conditions. It has a team of qualified healthcare professionals who review a person’s medical information. The company also has a licensed pharmacy that offers both generic and brand name drugs.

A person will first need to do an online health visit that focuses on their symptoms and medical history. If the doctor deems treatment appropriate, the person will receive their prescription within 24 hours. The company offers free, 2-day shipping, which may be more convenient for some people than visiting a pharmacy.

It also offers free follow-up consultations to ensure that the medication is still working as intended.


Insurance providers do not typically cover the services, products, and medications that Roman offers. However, a person with insurance should check with their plan provider whether they may claim reimbursement.

Learn more about Roman.

Best range of ED medication: Hims

  • Sildenafil: starting from $3 per dose
  • Viagra: about $139 per dose
  • Cialis (tadalafil): about $958 per month

Hims offers a range of ED medications and puts people in contact with licensed medical professionals who ensure that they receive tailored treatment.

The company offers free shipping on prescriptions and ongoing care from its medical team at no additional cost.


Insurance plans will not cover Hims products, but the company states that its products are accessible to consumers as it prices them 50–80% below retail cost.

Learn more about Hims.

Best for a free consultation: Optum Store

  • Sildenafil: starting from $6 per dose
  • Viagra: starting from $80 per dose
  • Tadalafil: starting from $7 per dose
  • Cialis: starting from $17 per dose

Optum Store and Medical News Today are owned by RVO Health.

Optum Store can provide medications for a variety of conditions, including ED. It offers a free consultation so a person can discuss which ED medication is right for their circumstances with a qualified healthcare professional.

The company offers delivery direct to a person’s home. People can choose between standard or expedited delivery for $5.99 and $9.99, respectively. However, expedited shipping is only available for returning customers.

Standard delivery takes approximately 2-7 business days, whereas expedited shipping takes 2 business days.


Optum Store only accepts insurance from OptumRX. However, people may be able ot receive reimbursement from their insurance provider.

The company does accept FSA and HSA cards.

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.

When a pharmaceutical company develops a new drug, it may have exclusivity for a specific period, which can last for years. Once this period of exclusivity elapses, competitors are free to market generic versions of a drug.

Generic versions must contain the same active ingredients as the brand-name drug. The active ingredient is the element of a medication that makes it effective against whatever it is treating.

The Food and Drug Administration (FDA) allows differences in inactive ingredients, but drug companies must prove that they do not interfere with the function, effectiveness, or safety of the drug.

Viagra is the brand name version of sildenafil. Since its exclusivity period expired in April 2020, generic versions of sildenafil have been available from alternative drug companies. These are generally available at a lower cost.

One observable difference between Viagra (brand name) and sildenafil (generic) is the pill’s appearance. While Viagra pills are blue, sildenafil pills are white. Both medications are safe and effective.

A person should contact a doctor for a sildenafil prescription, as the drug is not available over the counter.

It is vital for a person to talk with a doctor if they take other medications, as these may interact with sildenafil. Medications that may negatively interact with sildenafil include those for blood pressure.

Anyone who experiences any of the following side effects when using sildenafil should contact a doctor right away:

Some other potential adverse reactions associated with sildenafil include low blood pressure and hearing loss.

Below are some common questions relating to sildenafil and ED.

What is the difference between sildenafil and Viagra?

Viagra and sildenafil contain the same active ingredient — sildenafil citrate. Viagra is the brand name version of the medication, whereas sildenafil is the generic version, which is typically more cost-effective.

How often can you take sildenafil?

Individuals should not exceed the prescribed dosage, which generally means not taking more than one pill daily. However, if a doctor has advised a person to microdose their prescription, they may take smaller doses of sildenafil more frequently.

A person needs to follow their recommended dosage instructions.

Can you take sildenafil with other medications?

A person cannot take sildenafil if taking nitrate medication to treat angina or high blood pressure, as it can further lower their blood pressure.

If a person takes sildenafil for pulmonary arterial hypertension, they cannot take any PDE5 inhibitors, including Viagra.

Individuals should not use sildenafil alongside other ED medications or devices.

What happens if you take too much sildenafil?

If a person takes too much sildenafil, it can cause a persistent and painful erection. Other side effects may include blurred vision and chest pain. If this happens, a person should seek immediate medical aid.

What happens if you miss a dose?

If a person is taking sildenafil to treat ED, they do not need to worry about missing a dose. They should not take more than one tablet in a 24-hour period.

If they are using sildenafil for other medical purposes, such as for pulmonary arterial hypertension, the person should take the missed dose as soon as they remember, unless it is close to the time of the next dose. In this case, they should leave out the missed dose and continue with the next one instead.

A person must never take two doses at the same time or take an extra dose to make up for the missed one.

Does sildenafil get you hard?

Sildenafil should not cause an erection without sexual arousal. However, if a person takes this medication as a healthcare professional directs, the sildenafil should help a person to develop an erection.

How long does it take for sildenafil to kick in?

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

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

Despite its status as a generic drug, it 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.