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Viagra (Sildenafil): Uses, Benefits and Side Effects

Kelly Brown MD, MBA

Reviewed by Kelly Brown MD, MBA

Written by Geoffrey Whittaker

Published 04/08/2021

Updated 05/19/2024

Whether you’re a senior in high school or a senior-living resident, you’ve likely heard of Viagra® (sildenafil) — the original medication for erectile dysfunction (ED). Most men and women know at least vaguely what Viagra does, but not everyone knows how it does it.

So, what is Viagra, exactly, and how does it work?

Below, we’ll explain the origin story of Viagra, what this boner-benefitting pill can do, the benefits of Viagra for men, and the potential side effects of taking it.

Viagra is a medication for erectile dysfunction that can help adult men of all ages. This prescription drug is taken as needed to get and maintain erections hard enough for sexual intercourse. As long as it’s used as directed, it’s considered safe and effective.

What is sildenafil used for? Generic sildenafil (and brand-name Viagra) is a medication for the treatment of erectile dysfunction, Raynaud’s phenomenon, and pulmonary arterial hypertension.

To understand how Viagra works, we need to look at ED briefly.

The muscles regulating blood flow and supporting erections after sexual stimulation can sometimes malfunction. This is thanks to an enzyme called phosphodiesterase type 5 (PDE5). Viagra inhibits PDE5 and acts as a vasodilator (something that dilates blood vessels and increases blood flow). 

A single tablet of sildenafil can do that — typically, one dose is all that’s required to produce a firmer, longer-lasting erection. Studies have shown a 70 to 80 percent success rate in patients who use this treatment.

Since 1998, the Pfizer-created drug sildenafil citrate has been a reliable treatment for the management of erectile dysfunction. But the active ingredient began its clinical journey as a medication intended to treat hypertension (high blood pressure) and angina (chest pain due to high blood pressure).

Sildenafil can still be used to treat hypertension, but today, the primary use of this PDE5 inhibitor is to remedy erectile dysfunction. Other first-line treatment options for blood pressure and heart disease are now considered before Viagra.

Plenty of claims have been made about the health benefits of Viagra for men. Sildenafil’s ability to increase blood flow makes the medication useful for managing other conditions.

Some sources suggest Viagra might make you last longer in bed, and others say it’s good for heart health. But while this medication can help with the management of erectile dysfunction, it’s not a one-stop shop for every sexual improvement you’d like to achieve.

With that in mind, you should know that Viagra won’t increase penis size, it may not boost your sex drive, and it hasn’t really been shown to prevent tiredness during sex. We’re not just saying that, either — a study on 60 men confirmed this.

Not all claims about Viagra have been supported by enough science to convince us — let alone the FDA (U.S. Food and Drug Administration) — of their validity.

There are a few other potential uses for sildenafil.

Viagra might help with:

  • Pulmonary arterial hypertension

  • Mountain sickness

  • Raynaud’s phenomenon

  • Heart disease

Below, we’ll explain the different sildenafil uses and how the medication might affect people with these conditions.

Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a serious condition that happens when the tiny vessels in your lungs narrow, resulting in high blood pressure.

Normally, the pulmonary artery supplies oxygen-filled blood from the lungs to the heart. But with this condition, the arteries are blocked, narrowed, or even destroyed, preventing healthy blood flow.

When that happens, blood pressure in the lungs increases, and the heart has to work harder to get blood through those tiny arteries — a process that can eventually tire out the lungs, potentially causing heart failure.

Viagra can help reduce blood pressure in the lungs within its role as a vasodilator — essentially, it can do for your lungs what it does for your penis. Sildenafil lowers blood pressure in the lungs so the heart doesn’t have to work as hard to pump blood away.

In a study comparing the effects of sildenafil and bosentan (a popular drug for managing PAH), sildenafil was found to be just as effective in managing the condition when combined with other therapies, like diuretics (medications that make you pee more to reduce fluid buildup).

Sildenafil for managing PAH is marketed under the name Revatio® with a particular dosage. It’s one of several FDA-approved treatments for the condition.

Mountain Sickness

Beyond a massive adrenaline rush, mountain climbing can come with a bout of altitude sickness, sometimes called mountain sickness.

Some reports say that since Viagra can widen blood vessels, it can increase blood flow through the heart, permitting more oxygen to the lungs and improving oxygen supply to the rest of the body.

One study tested this theory in ten cyclists riding at a high altitude. The medication was found to improve heart function and blood oxygen levels. It also enhanced performance levels in some participants.

That said, ten cyclists is hardly enough to convince us (let alone the FDA) to approve something as a treatment.

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Raynaud’s Phenomenon

During a Raynaud’s phenomenon (sometimes called a Raynaud’s attack), blood flow to the hands and feet is reduced. This makes them feel numb and cold.

Episodes can happen when you’re exposed to cold temperatures or are under emotional stress.

Raynaud’s phenomenon is usually more annoying than serious — although severe (and rare) cases can lead to tissue death in the hands or feet, which could require amputation.

Viagra’s ability to decrease the number of attacks in people affected by the phenomenon was confirmed in a small study. Participants started off on 100 milligrams of sildenafil for three days before moving on to 200 milligrams for two days. The medication seemed to treat the condition and was well tolerated.

Viagra is definitely not an appropriate first-line treatment for Raynaud’s phenomenon, but in situations where more common medications have failed, it could be an option.

Heart Disease

One of the most common forms of heart failure happens when the left heart ventricle (responsible for pumping oxygen-rich blood to the rest of the body) can’t effectively do its job. This causes blood to back up into the lungs, which can lead to fluid buildup.

In at least one study, regular long-term use of sildenafil was shown to improve left ventricle function while strengthening the structure of a failing left ventricle.

Sildenafil’s role as a PDE5 inhibitor might help prevent the thickening of heart muscles, a feature that makes it difficult to pump blood. Viagra has also shown real promise for increasing the amount of blood pumped by the heart, but more research is needed.

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Like any medication, side effects of Viagra may come with its many benefits. Still, Viagra is safe when used as directed.

Viagra may cause common side effects, including:

  • Flushing

  • Nasal congestion

  • Headaches

  • Back pain and other body aches

  • Indigestion (upset stomach or constipation)

These are usually mild and often go away over time. Not sure if something is a side effect of Viagra? Check out our Viagra (sildenafil) side effects guide for a more comprehensive list.

What you really need to watch out for are the more serious side effects, which may include:

  • Eye problems, like blurred vision, retinitis pigmentosa, or vision loss

  • Chest pain

  • Loss of hearing

  • Priapism (painful, prolonged erections)

Sildenafil could also cause an increased risk of heart attack or other heart problems.

If you have an irregular heartbeat, hearing loss, vision loss, an allergic reaction, Peyronie’s disease, or sickle cell anemia, or are being treated for leukemia or other medical conditions, share this with your healthcare provider.

A word on sildenafil drug interactions: Mixing antihypertensive prescription drugs (hypertension meds) with Viagra may cause low blood pressure. Since the medication has blood pressure-lowering abilities, pairing it with another drug that reduces blood pressure could lead to a dangerous or potentially fatal drop in blood pressure.

Likewise, Viagra shouldn’t be combined with antiretroviral drugs used to treat HIV/AIDS, as it can cause an increased concentration of sildenafil in the body. Breastfeeding women shouldn’t take this medication, either.

Other medications that could cause sildenafil drug interactions include:

  • Riociguat

  • Saquinavir

  • Antifungals (like itraconazole or ketoconazole)

  • Antibiotics (like erythromycin)

Because of the risks of this medication, people taking alpha-blockers, over-the-counter nitrate supplements (like amyl nitrate, isosorbide mononitrate, isosorbide dinitrate, or nitroglycerin) or recreational drugs (like “poppers”) should tell a healthcare professional before taking Viagra.

Find answers to frequently asked questions about Viagra and sildenafil below.

How Long Does Viagra Take to Work?

Viagra usually starts working 30 to 60 minutes after taking it. But simply swallowing the little blue pill won’t automatically give you an erection — you still have to be sexually aroused, either through mental or physical stimulation.

Can You Make Viagra Work Faster?

Some guys might feel the effects of Viagra faster when they take the pill on an empty stomach. Taking it with food, particularly high-fat foods like a burger and fries, can slow it down or even make it less effective.

Stendra® (avanafil) is a faster-acting ED medication. This one can start working just 15 minutes after you take it.

For more on how to take Viagra for best results, check out our blog.

How Long Does Viagra Last?

This medication works for about four hours. So after taking Viagra, you should be able to get and maintain erections hard enough for sex (again, with stimulation) within that window. 

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Viagra has made its way into medicine cabinets the world over as a trusted medication for erectile dysfunction and cardiovascular health. We know sexual activity is supposed to be somewhat off the cuff, but you still shouldn’t take it with abandon. 

Using Viagra only as directed by a healthcare provider is vital for avoiding many potentially dangerous side effects that can occur when you go off-script with your prescription.

Interested in trying Viagra? Here are the most important things to know:

  • Viagra is a proven treatment for erectile dysfunction. While it may not do anything for your sexual experience in terms of libido, it can have incredible effects if you’re having problems getting and maintaining erections.

  • It’s not the only ED med. Other medications for ED, like Cialis® (tadalafil), Levitra® (vardenafil), and Stendra (avanafil), may also help.

  • Follow the guidance of a medical professional. Always consult a trusted healthcare professional for medical advice on the best ways to use this drug — and let them know about any other meds or supplements you’re taking.

  • You can get Viagra and generic sildenafil online. You can get a prescription for ED medication on our telehealth platform, including Viagra, sildenafil, and our chewable ED meds hard mints. 

There are a bunch of informative articles on our blog if you want to learn more about Viagra and sexual health. We can also help you get easy access to affordable Viagra from the comfort of your home.

Explore your options from Hims today.

12 Sources

  1. Ghofrani HA, et al. (2006). Sildenafil: from angina to erectile dysfunction to pulmonary hypertension and beyond.
  2. Guazzi M, et al. (2011). PDE5 inhibition with sildenafil improves left ventricular diastolic function, cardiac geometry, and clinical status in patients with stable systolic heart failure: results of a 1-year, prospective, randomized, placebo-controlled study.
  3. Herrick AL, et al. (2011). Modified-release sildenafil reduces Raynaud’s phenomenon attack frequency in limited cutaneous systemic sclerosis.
  4. HIGHLIGHTS OF PRESCRIBING INFORMATION : VIAGRA® (sildenafil citrate) tablets, for oral use. (n.d.). https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/20895s039s042lbl.pdf.
  5. Hirata K, et al. (2005). Effect of Sildenafil on Cardiac Performance in Patients With Heart Failure.
  6. Hsu AR, et al. (2006). Sildenafil improves cardiac output and exercise performance during acute hypoxia, but not normoxia.
  7. Hutchings DC, et al. (2018). Phosphodiesterase-5 inhibitors and the heart: compound cardioprotection?.
  8. McCullough AR. (2002). Four-year review of sildenafil citrate.
  9. Mondaini N, et al. (2003). Sildenafil does not improve sexual function in men without erectile dysfunction but does reduce the postorgasmic refractory time.
  10. Murdoch D. (2010). Altitude sickness.
  11. Oldroyd SH, et al. (2022). Pulmonary Hypertension.
  12. Wilkins MR, et al. (2005). Sildenafil versus Endothelin Receptor Antagonist for Pulmonary Hypertension (SERAPH) study.
Editorial Standards

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references. See a mistake? Let us know at [email protected]!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment. Learn more about our editorial standards here.

Kelly Brown MD, MBA
Kelly Brown MD, MBA

Dr. Kelly Brown is a board certified Urologist and fellowship trained in Andrology. She is an accomplished men’s health expert with a robust background in healthcare innovation, clinical medicine, and academic research. Dr. Brown was previously Medical Director of a male fertility startup where she lead strategy and design of their digital health platform, an innovative education and telehealth model for delivering expert male fertility care.

She completed her undergraduate studies at University of North Carolina at Chapel Hill (go Heels!) with a Bachelor of Science in Radiologic Science and a Minor in Chemistry. She took a position at University of California Los Angeles as a radiologic technologist in the department of Interventional Cardiology, further solidifying her passion for medicine. She also pursued the unique opportunity to lead departmental design and operational development at the Ronald Reagan UCLA Medical Center, sparking her passion for the business of healthcare.

Dr. Brown then went on to obtain her doctorate in medicine from the prestigious Northwestern University - Feinberg School of Medicine and Masters in Business Administration from Northwestern University - Kellogg School of Management, with a concentration in Healthcare Management. During her surgical residency in Urology at University of California San Francisco, she utilized her research year to focus on innovations in telemedicine and then served as chief resident with significant contributions to clinical quality improvement. Dr. Brown then completed her Andrology Fellowship at Medical College of Wisconsin, furthering her expertise in male fertility, microsurgery, and sexual function.

Her dedication to caring for patients with compassion, understanding, as well as a unique ability to make guys instantly comfortable discussing anything from sex to sperm makes her a renowned clinician. In addition, her passion for innovation in healthcare combined with her business acumen makes her a formidable leader in the field of men’s health.

Dr. Brown is an avid adventurer; summiting Mount Kilimanjaro in Tanzania (twice!) and hiking the incredible Torres del Paine Trek in Patagonia, Chile. She deeply appreciates new challenges and diverse cultures on her travels. She lives in Denver with her husband, two children, and beloved Bernese Mountain Dog. You can find Dr. Brown on LinkedIn for more information.

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