Drug Info

How does Viagra work?

Cropped SingleCare logo By | January 14, 2020
Medically reviewed by Lindsey Hudson, APRN, NP-C

Taking Viagra for the first time often sparks a series of questions. How does Viagra work? What can I expect? How long does Viagra last? What kind of side effects are normal? Which side effects require medical attention? Here are answers to some frequently asked questions about the little blue pill.

What is Viagra?

Viagra (sildenafil) is a prescription drug used to treat erectile dysfunction (ED) in men. Viagra can’t cure ED or increase sexual desire. Instead, it relaxes muscles and increases blood flow to cause an erection.

Manufactured by Pfizer, Viagra is a brand name for the generic medication sildenafil citrate. The U.S. Food and Drug Administration (FDA) has approved Viagra to treat sexual impotence. Sildenafil may also treat pulmonary arterial hypertension. Viagra is a vasodilator that is only available by prescription.

You cannot purchase Viagra over the counter in the U.S.

How does Viagra work?

Viagra works by relaxing muscles in blood vessel walls to help increase blood flow to the penis, making it easier to get and maintain an erection. Viagra is only effective if there is sexual stimulation, such as that occurring during sexual intercourse. When stimulation first happens, Viagra helps increase blood flow to the penis and then works to help maintain an erection.

According to the Boston University School of Sexual Medicine, erectile dysfunction affects up to 52% of men between the ages of 40-70, many of whom turn to erectile dysfunction medications to help with their symptoms. Viagra is a type of erectile dysfunction drug called a phosphodiesterase 5 inhibitor. PDE5 inhibitors keep a particular enzyme called phosphodiesterase type-5 (PDE5) from acting too quickly. If PDE5 acts slower, then a substance that’s responsible for relaxing muscles and widening blood vessels can do its job.

Viagra will not be as effective for people with certain conditions. You may not get the full benefits of Viagra if you are sick, fatigued, or intoxicated. Alcohol can worsen the side effects of viagra and potentially make erectile dysfunction worse.

You should take Viagra on an empty stomach about one hour before sex. It starts working within 30 to 60 minutes, but an erection requires sexual stimulation.

“Some patients experience the effects of Viagra within 20 to 30 minutes after taking the medication,” says Amber Williams, Pharm.D., a compounding pharmacist at Family Pharmacy in Sarasota. “However, if the dose is taken with a high-fat meal, the peak response may be delayed for up to 60 minutes. In most patients, the effects of Viagra will last for up to two hours. A duration of two hours or less indicates that an appropriate dose was taken. If the duration is greater than four hours, medical attention should be sought out immediately to avoid damaging effects on the tissues.”

How long does Viagra last?

The amount of time that Viagra will last depends on many factors. Dosage, age, and overall health are just some of the factors that can impact how well Viagra works and lasts for someone. A smaller dosage of Viagra (recommended for older adults) means that the drug won’t last as long.

The average dose of Viagra is 25-100 mg, taken 30 to 60 minutes, or up to four hours before sexual activity. For adults over the age of 65, the recommended dose is 25 mg. Many older adults have slower metabolisms, which means that a lower dose may last longer for them in comparison to a younger person taking a small dose.

Take Viagra before sexual activity, as it takes time for Viagra to absorb into the bloodstream. It’s unlikely that Viagra will help you last longer during sexual intercourse. However, some men—depending on their metabolism—may experience multiple erections while Viagra is in their system. Once it starts working, Viagra typically lasts for up to four or five hours. If you do experience an erection that lasts longer than this (priapism) or is painful, it may be time to seek medical advice.

Viagra won’t necessarily help you recover faster after orgasm. Recovery time (called the refractory period) varies for each individual. Consuming alcohol while taking Viagra can make the medication less effective by decreasing blood flow to the penis.

For people with certain medical conditions, Viagra might not last as long. Feelings of anxiety, depression, or nervousness often cause Viagra not to last as long or be as effective. Having a heart problem, heart disease, diabetes, or other nervous system problems can also cause Viagra not to last as long.

Certain medications may interact negatively with Viagra and interfere with its effectiveness. Drugs that lower blood pressure can interact with Viagra to cause dangerously low blood pressure. Don’t take Viagra with any medication that contains nitrates, which includes street drugs called “poppers” like amyl nitrate and butyl nitrate. Antifungal and antiviral medications may increase the amount of Viagra in the bloodstream, which can lead to toxicity. Talking with your healthcare provider is the best way to determine if Viagra will cause any drug interactions.

How do you know if you need Viagra?

Knowing when to speak to a doctor about getting Viagra can be challenging. Having trouble getting an erection doesn’t necessarily mean that you need to take Viagra. Viagra won’t cure erectile dysfunction. Therefore, it’s essential to look at the potential underlying causes of impotence.

Some men might not be able to get or maintain an erection for psychological reasons. If you don’t have a desire to have sex with your partner, this could be causing your ED. Talk to a counselor individually or see a therapist with your sexual partner to resolve underlying psychological issues.

The best way to know if you will benefit from taking an erectile dysfunction medication like Viagra is to consult your healthcare provider. They can perform a physical examination and rule out medical conditions that may be causing ED. Some of these health conditions include diabetes, high cholesterol, or high blood pressure.

If you have no underlying psychological or health issues and have trouble getting and maintaining an erection that’s hard enough for sex, you may benefit from taking Viagra.

Once you’ve talked with a healthcare provider, he or she may give you a prescription for Viagra.

If you can’t get to your doctor, there are other options available. “Sildenafil is available online through validated telemedicine sites that connect you to licensed doctors,” says Dr. Williams. “These doctors will conduct an online visit and review your current health status to determine if sildenafil is an option for you. If you are a good candidate, your prescription may be shipped to you conveniently.”

But take caution with where you purchase it: Even though Viagra is available online, it’s one of the most counterfeited drugs in the world. Some counterfeit pills contain printer ink, antibiotics, and even amphetamines. Get a valid prescription and purchase Viagra from a U.S.-based pharmacy accredited by the Verified Internet Pharmacy Practice Sites to avoid counterfeit Viagra.

There are other prescription medications besides Viagra that treat erectile dysfunction. If you aren’t getting the results you want, it may be time to talk to your healthcare provider about other treatment options.

Cialis (tadalafil) and Levitra (vardenafil) also treat ED. The active ingredient that’s in generic Viagra, sildenafil citrate, is also in the medication Revatio. Revatio (sildenafil) treats pulmonary arterial hypertension (PAH), a condition where blood pressure in the lungs is too high.

What are the side effects of Viagra?

As with any medication, there is always the potential for side effects. The following list of side effects is not comprehensive. Speak with a healthcare provider to determine if Viagra is the right medication for you. Here’s a list of some of the most common Viagra side effects that you may experience:

  • Flushing
  • Lightheadedness
  • Headache
  • Back pain
  • A runny or stuffy nose
  • Indigestion

Although it’s rare, Viagra can sometimes cause serious side effects. If you experience the following effects, stop taking Viagra and contact your healthcare provider immediately.

  • A sudden loss of vision or hearing
  • An erection that’s painful and lasts more than four hours
  • Chest pain after taking Viagra at the onset of sexual activity

In extreme cases, Viagra has caused heart attacks in people with prior heart conditions.

Drinking excessive amounts of alcohol while taking Viagra can significantly increase the risk of experiencing any of the side effects listed above. Talk to a healthcare provider for a comprehensive list of Viagra side effects and learn more about whether taking Viagra is right for you.