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Viagra® (Sildenafil) Side Effects

Mike Bohl, MD, MPH, ALM

Reviewed by Mike Bohl, MD, MPH, ALM

Written by Rachel Sacks

Published 07/11/2019

Updated 01/16/2024

You have a big date night planned and want everything to go smoothly. But if you deal with erectile dysfunction (ED) on occasion — no big deal, a lot of guys do — you might want to have some sildenafil (better known by its brand name Viagra®) on hand.

Nicknamed the “little blue pill,” Viagra is the most well-known erectile dysfunction medication out there. But despite how ubiquitous it is, many guys probably don’t stop to think about sildenafil side effects.

While sildenafil is generally safe and effective for men, there’s still a possibility of experiencing mild side effects, as well as rarer but more serious effects.

Whether this is your first time using sildenafil, you’re a regular user or it’s just been a while since you last needed it, it’s always good to know as much as you can about a medication — including the side effects.

Most of the Viagra side effects are mild and transient (meaning they tend to fade away as the medication exits your body), although some can become serious if you use other medications or have a pre-existing health condition.

Below, we’ve listed the most common side effects of sildenafil and Viagra precautions you should know about.

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The Most Common Side Effects of Sildenafil

Sildenafil is a type of prescription drug known as a PDE5 inhibitor. Sildenafil and other PDE5 inhibitors prevent the function of an enzyme called phosphodiesterase type 5.

By blocking the PDE5 enzyme, sildenafil helps increase blood flow to your penis for stronger erections. 

Viagra, like every medication, has the potential to cause side effects. Typically, these side effects occur while the medication is active in your body (generally three to five hours), although some may continue for several hours after Viagra’s active effects wear off.

The most common side effects of sildenafil are generally very mild, with more than 94 percent of patients feeling satisfied with the treatment and reporting few side effects — which makes sildenafil a safe ED medication.

You’re more likely to experience sildenafil side effects if you take a higher dose, although they’re still generally mild and short-lasting.

Regardless of your dosage, the most common side effects of sildenafil you’re likely to experience include:

  • Headaches

  • Back pain

  • Nasal congestion (rhinitis)

  • Dizziness

  • Facial flushing

  • Indigestion or heartburn (dyspepsia)

  • Nausea

  • Visual changes (blurred vision or sensitivity to light)

  • Low blood pressure

  • Rash

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Less Common, More Serious Viagra Side Effects

Although serious side effects from Viagra are highly uncommon, they can still happen. Viagra has several of these rare side effects, including allergic reaction, priapism and damage to the nerve that delivers electrical impulses from your eyes to your brain. 

It’s important to pay close attention to the symptoms of these side effects and notify your healthcare provider if you experience any issues.

Priapism (Prolonged and/or Painful Penile Erection)

Priapism is a serious condition in which you experience a painful and prolonged erection that lasts for several hours without any sexual stimulation. It can result in permanent damage to the erectile tissues inside your penis if it’s left untreated.

Compared to other Viagra side effects, priapism is very uncommon. However, priapism can cause many severe complications, including ischemia, hypoxia, cavernosal acidosis and permanent damage to the erectile tissues in your penis.

If you develop a painful penile erection that persists for several hours, especially with little or no sexual stimulation, it’s important to seek medical advice from a healthcare professional as soon as possible.

Damage to the Optic Nerve

Although it’s extremely rare, erectile dysfunction drugs such as Viagra are linked to damage to the optic nerve, specifically nonarteritic anterior ischemic optic neuropathy (NAION).

NAION is a serious medical condition that can result in permanent damage to the eyes, including vision loss.

This issue affects a very small percentage of men who use Viagra, but having existing eye issues or a "crowded" optic disc may put you at a higher risk.

In a review published in the International Journal of Clinical Practice in 2006, researchers found that approximately 2.8 cases of NAION occur per 100,000 patient-years of Viagra use, which means it’s pretty unlikely you’ll get this rare side effect.

To reduce your risk of developing NAION, it’s important to inform your healthcare provider of any existing vision-related health issues before using Viagra, and get immediate medical attention if you experience any loss of vision while using Viagra or similar medications to treat ED.

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Sudden Loss of Hearing

An extremely small percentage of men who used Viagra have reported a condition known as sudden sensorineural hearing loss (SSHL). This condition involves damage to the inner ear that can, in some cases, cause permanent loss of hearing. 

In addition to hearing loss, Viagra can cause other hearing-related conditions, such as ringing in the ears (tinnitus).

Hearing issues from Viagra are uncommon, but it’s important to tell your healthcare provider if you experience any changes in your hearing after taking Viagra, such as sudden loss of hearing or reduced hearing sensitivity.

Sildenafil Interactions & Precautions

While you may not be able to avoid some of the more common side effects of sildenafil, there are some other Viagra warnings to take note of.

Specifically, you should be aware of sildenafil drug interactions with some medications, such as those used to treat high blood pressure, heart disease and other cardiovascular health issues. 

These medications can lower blood pressure when used with Viagra, so be sure to tell your healthcare provider if you’re taking any of them:

  • Nitrates such as nitroglycerin, isosorbide dinitrate or isosorbide mononitrate

  • Alpha-blockers

  • Recreational drugs that contain nitrites (called “poppers”)

  • Other PDE5 inhibitors, including Revatio or other ED or pulmonary arterial hypertension treatments

There are also a few foods to avoid when taking Viagra, including grapefruit juice (which can affect how Viagra is metabolized in the body), high-fat meals (which can delay Viagra’s absorption) and excessive alcohol.

Certain medical conditions may also increase your likelihood of developing side effects from Viagra and other ED medications. To keep yourself safe while using Viagra, it’s important to inform your healthcare provider about any pre-existing conditions before you consider this medication, such as:

  • Any type of heart problems, such as heart failure, angina, narrowing of the aortic valve, irregular heartbeat or a previous heart attack or stroke

  • Pulmonary hypertension (high blood pressure in the blood vessels that supply your lungs), uncontrolled high blood pressure or low blood pressure

  • Any type of medical condition that affects your blood cells, such as leukemia, sickle cell anemia or multiple myeloma

  • Any type of eye problem or vision loss, such as non-arteritic anterior ischemic optic neuropathy or retinitis pigmentosa, a genetic eye disease

  • A deformed penis shape or a condition such as Peyronie’s disease, which involves damage to the tissue inside your penis

  • Bleeding problems, liver problems, kidney problems (especially if you’re on dialysis) or stomach ulcers

While it may be tempting to pop a pill “just in case,” using Viagra without ED can be risky and cause unwanted side effects.

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Understanding Sildenafil Side Effects

One of the downsides of taking any medication is that you might experience side effects — and Viagra (or sildenafil) is no exception. But what should you expect with the little blue pill and what might be cause for concern?

  • Viagra, which contains the active ingredient sildenafil citrate, is a type of medication known as a PDE5 inhibitor. This type of medication improves blood flow and helps create erections firm enough for sexual activity.

  • Sildenafil can cause mild side effects, the most common of which include headaches, back pain, nasal congestion, dizziness, facial flushing, nausea, changes in vision and more.

  • More serious side effects are rare but possible. These include damage to the optic nerve, sudden loss of hearing and priapism, which is a prolonged, painful erection.

If you’re still looking for more info on Viagra, you can read this guide on how to take Viagra for the best results, or learn if you can take Viagra daily and whether there’s such a thing as too much sildenafil. And in terms of comparing Viagra vs sildenafil, know that both medications work the same way.

Viagra also isn’t the only effective erectile dysfunction medication on the market. 

Vardenafil, the active ingredient in Levitra, starts working in approximately the same amount of time as sildenafil and should be taken one hour before sex.

You can also ask your healthcare provider about Stendra® (avanafil). A second-generation ED treatment, avanafil is the fastest-acting medication that produces noticeable effects in 15 to 30 minutes.

Or you can try Cialis® (tadalafil). Known as the “weekend pill,” Cialis can last for 36 hours.

While many of these medications are available as oral tablets, they also come as chewable hard mints.

If you’re interested in exploring erectile dysfunction treatments, you can check them out here or talk to a licensed healthcare provider to learn more.

7 Sources

  1. McMurray, J. G., Feldman, R. A., Auerbach, S. M., Deriesthal, H., Wilson, N., & Multicenter Study Group (2007). Long-term safety and effectiveness of sildenafil citrate in men with erectile dysfunction. Therapeutics and clinical risk management, 3(6), 975–981. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2387281/
  2. Huang, S. A., & Lie, J. D. (2013). Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction. P & T : a peer-reviewed journal for formulary management, 38(7), 407–419. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3776492/
  3. VIAGRA- sildenafil citrate tablet, film coated. (2017, August). Retrieved from https://www.accessdata.fda.gov/spl/data/40578e70-350a-4940-9630-55d90989c146/40578e70-350a-4940-9630-55d90989c146.xml
  4. Gorkin, L., Hvidsten, K., Sobel, R. E., & Siegel, R. (2006). Sildenafil citrate use and the incidence of nonarteritic anterior ischemic optic neuropathy. International journal of clinical practice, 60(4), 500–503. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1448698/
  5. LEVITRA (vardenafil hydrochloride) tablets, for oral use. (2014, April). Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/021400s017lbl.pdf
  6. STENDRA- avanafil tablet. (2017, August). Retrieved from https://www.accessdata.fda.gov/spl/data/41d308f4-9a6a-48bb-b7a0-d63da9818078/41d308f4-9a6a-48bb-b7a0-d63da9818078.xml
  7. CIALIS- tadalafil tablet, film coated. (2017, May). Retrieved from https://www.accessdata.fda.gov/spl/data/05dbd8b6-1b9d-436a-a67c-8a16713f753f/05dbd8b6-1b9d-436a-a67c-8a16713f753f.xml
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.

Mike Bohl, MD, MPH, ALM

Dr. Mike Bohl is a licensed physician and the Director of Scientific & Medical Content at a stealth biotech startup. Prior to joining Hims & Hers, Dr. Bohl spent several years in digital health focusing on patient education. He has also worked in medical journalism for The Dr. Oz Show and Sharecare and has served on the Medical Expert Board of Eat This, Not That!.

Dr. Bohl obtained his Bachelor of Arts and Doctor of Medicine from Brown University, his Master of Public Health from Columbia University, and his Master of Liberal Arts in Extension Studies—Journalism from Harvard University. He is currently pursuing a Master of Business Administration and Master of Science in Healthcare Leadership at Cornell University. Dr. Bohl trained in internal medicine with a focus on community health at NYU Langone Health.

Dr. Bohl is Certified in Public Health by the National Board of Public Health Examiners, Medical Writer Certified by the American Medical Writers Association, a certified Editor in the Life Sciences by the Board of Editors in the Life Sciences, a Certified Personal Trainer and Certified Nutrition Coach by the National Academy of Sports Medicine, and a Board Certified Medical Affairs Specialist by the Accreditation Council for Medical Affairs.

In addition to his written work, Dr. Bohl has experience creating medical segments for radio and producing patient education videos. You can find Dr. Bohl on LinkedIn for more information

Dr. Bohl lives in Manhattan and enjoys biking, resistance training, sailing, scuba diving, skiing, tennis, and traveling. You can find Dr. Bohl on LinkedIn for more information.

Education

  • Bachelor of Arts, Egyptian and Ancient Western Asian Archaeology. Brown University |

  • Doctor of Medicine. |

  • Master of Public Health, General Public Health. |

  • Master of Liberal Arts, Journalism. |

  • Master of Business Administration. | (anticipated 2024)

  • Master of Science, Healthcare Leadership. | (anticipated 2024)

Training

  • NYU Internal Medicine Residency—Brooklyn Community Health Track. |

Certifications

  • Certified in Public Health.

  • Medical Writer Certified.

  • Editor in the Life Sciences.

  • Certified Personal Trainer.

  • Certified Nutrition Coach.

  • Board Certified Medical Affairs Specialist. Accreditation Council for Medical Affairs

  • Digital Storytelling Graduate Certificate.

  • Marketing Management and Digital Strategy Graduate Certificate.

Publications

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