How Does Sildenafil Work? Uses and Benefits

Published March 10th, 2021 by Erik Rivera
Fact Checked by
Camille Freking
Updated Date: Jun 14th, 2022

The introduction of Viagra to the U.S. market in the late 1990s provided a glimmer of hope for the tens of millions of adult men suffering from erectile dysfunction -- at least until they saw the cost of the drug.

At upwards of $60 per pill, Viagra was largely unaffordable for many people until the generic version of the drug, sildenafil citrate, was introduced in 2017. 

Sildenafil is just as effective at treating erectile dysfunction as Viagra, but how does sildenafil work?

What is sildenafil?

Sildenafil may not be as well known as Viagra, but the generic name for the active ingredient in the “little blue pill” works the same way and treats the same conditions as the brand name drug. 

Generic sildenafil was first introduced to the market in December 2017 and is sold under the brand names Viagra and Revatio.

Today, sildenafil is manufactured by numerous companies and sold in a variety of forms. 

Conditions commonly treated with sildenafil include erectile dysfunction, Rayaud’s phenomenon, high blood pressure, and pulmonary hypertension.

The most common use of sildenafil is for the treatment of erectile dysfunction.

What is erectile dysfunction and what causes it?

Erectile dysfunction, often called ED or male impotence, is a type of sexual dysfunction that occurs when a man has difficulty getting and/or keeping an erection that is hard enough for sex. 

There are many factors that contribute to erectile dysfunction, but at its core, the condition is caused by insufficient blood flow to the penis, which prevents an erection.

An estimated 30 million men in the U.S. suffer from ED, and the condition ranges in severity from occasional difficulty getting an erection to chronic issues with sexual dysfunction.

There are many different medical conditions that can cause ED, including depression, diabetes, heart disease, high cholesterol, obesity, high blood pressure, prostate cancer treatment, and spinal cord injury.

Smoking, drinking alcohol, high stress levels, illegal drug use, and the use of certain prescription drugs can also contribute to ED.

Some medications, including those used to treat high blood pressure, heart disease, and depression, can also cause ED.

ED is largely attributed to lifestyle factors, which means that the condition may be prevented or improved by making lifestyle changes. 

If you’re looking for ways to improve your circulation without over-the-counter or prescription medication, you can try:

  • Finding more ways to stay active
  • Quitting smoking
  • Reducing stress in your daily life
  • Managing your weight by eating whole foods and reducing portion sizes
  • Drinking less alcohol

If you’re experiencing ED, you should know that you’re not alone. Your doctor can help you effectively treat your symptoms.

How does sildenafil treat erectile dysfunction?

Sildenafil belongs to a class of drugs called phosphodiesterase type 5 inhibitors (PDE-5 inhibitors).

Viagra works to treat erectile dysfunction by inhibiting the action of an enzyme that causes blood to flow out of the penis, ending an erection. 

When using sildenafil, men are able to get and keep an erection that is hard enough for sexual intercourse by dilating blood vessels to enhance blood flow.

Sildenafil will not work without sexual stimulation, so there is no concern about having an erection at an inopportune time. 

What does sildenafil cost?

Sildenafil is the generic version of Viagra, which means that sildenafil is available at a much lower cost than Viagra. 

Sildenafil did not become available until December 2017, when Pfizer’s patent for Viagra expired.

Viagra initially cost approximately $60 per pill, but the release of generic sildenafil cut the cost in half to about $30 per pill. 

Today, a greater number of manufacturers are producing sildenafil, which has lowered the cost of the medication even further. Sildenafil can currently be purchased at a cost of about $4 per pill, which represents a savings of over 90 percent compared to the original price of Viagra. 

Most patients will find that sildenafil is covered by their commercial insurance, Medicare, or Medicaid plans, but it is possible to save even more by using pharmacy discount cards or paying cash. 

What are the benefits of using sildenafil?

Sildenafil is one of the most popular drugs in the United States for a reason.

In addition to the effective treatment offered by sildenafil for conditions like Raynaud’s Phenomenon, high blood pressure, pulmonary arterial hypertension, and angina pectoris, it is the first and most comprehensively studied FDA-approved medication for the treatment of erectile dysfunction, including ED caused by Peyronie's Disease. 

Sildenafil is a generic medication that offers the same treatment as the original brand name drug, Viagra, at a mere fraction of the cost.

While some patients are concerned about the quality and ingredients included in the generic form of medications like sildenafil, there is really no reason to be concerned. 

Generic drugs are subjected to the same rigorous testing and standards as brand name drugs like Viagra. All generic medications must be approved by the FDA in order to ensure their safety and effectiveness.

Generic medications use the same active ingredients as brand name drugs but may have differences in the inactive ingredients (ingredients that do not affect treatment) and cosmetic details like color, shape, and size of the medication.

Sildenafil is available in slightly smaller doses than brand name Viagra, which means that the medication can be more precisely prescribed based on the patient’s individual need.

Viagra is sold in 25 mg and 50 mg pills, while sildenafil comes in 20 mg tablets.

As a result, sildenafil can be prescribed in doses of  20 mg, 40 mg, 60 mg, 80 mg, and 100 mg, while Viagra is limited to treatment options of 25 mg, 50 mg, and 100 mg. 

The higher the dose of Viagra or sildenafil, the more likely patients are to experience side effects of viagra or sildenafil.

Lower doses of the drug may offer the desired effects without causing common side effects like headaches and nausea, and the wider variety of doses available for sildenafil means that patients do not have to take more of the drug than they need. 

Additionally, patients have more flexible dosing options with sildenafil, meaning they can take more of the medication than they otherwise might in a situation that causes anxiety, such as performance anxiety with a new partner or additional stress resulting in reduced sexual desire. 

How is sildenafil used to treat erectile dysfunction?

Sildenafil is not taken at the same time each day or even on a daily basis for most patients. Instead, sildenafil is used on an as-needed basis in advance of sexual activity.

Of course, predicting when sex will occur can be a challenge, but it is possible to take sildenafil as much as four hours and as little as one hour before intercourse. 

Sildenafil may work in as quickly as 30 minutes, but there are a number of factors that impact how quickly the medication takes effect, including other medications used by the patient, how recently large amounts of fat were eaten, and function of the kidneys and liver. 

Eating a high-fat meal within two to three hours of taking sildenafil is known to slow the action of the medication. 

Sildenafil should not be taken more frequently than once every 24 hours, and some patients will be able to take it less frequently based on their medical history or other medications they may be taking.

Are there any side effects associated with sildenafil?

Like any medication, there are side effects associated with the use of Viagra and its generic forms.

Men using Viagra should never use nitrates, a common heart problem medication, at the same time, as it can be fatal. 

The side effects most commonly associated with sildenafil are:

  • Headache
  • Flushing (feeling of warmth)
  • Muscle aches
  • Sensitivity to light
  • Nosebleeds
  • Heartburn
  • Diarrhea
  • Indigestion
  • Low blood pressure
  • Difficulty falling asleep or staying asleep
  • Numbness, burning, or tingling in the arms, hands, feet, or legs

Other rarely reported, serious side effects requiring immediate medical attention include:

  • Priapism - erections lasting longer than four hours
  • Sudden hearing decrease, hearing loss, or ringing in the ears
  • Dizziness or lightheadedness
  • Blurred vision
  • Sudden vision loss in one or both eyes, which is a symptom of a serious eye problem called non-arteritic anterior ischemic optic neuropathy (NAION)
  • Retinitis pigmentosa
  • Allergic reactions
  • Fainting
  • Itching or burning during urination
  • Rash
  • Chest pain
  • Worsening shortness of breath
  • Bleeding in the brain or lungs
  • Painful erection
  • High blood pressure
  • Heart attack
  • Stroke
  • Irregular heartbeat


Sildenafil works by inhibiting the action of an enzyme called PDE-5, which causes an erection to break down.

The medication is used up to four hours before sexual activity and as little as one hour before intercourse, and it is considered an effective treatment for ED

Sildenafil can be taken on an as-needed basis, is affordable, and allows men to fine-tune their treatment plan based on the recommended dose of sildenafil in order to minimize side effects.

Sildenafil, like Viagra, should be taken on an empty stomach. 

Grapefruit specifically can delay the absorption of sildenafil. It is safe for men suffering from sickle cell anemia and leukemia, and can possibly enhance the collection of blood stem cells. 

Other options for ED medications include tadalafil (Cialis) and vardenafil (Levitra).

These should only be used under the medical advice of a healthcare professional. 

Talk to your healthcare provider to see if sildenafil is right for you. 


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