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Viagra (Sildenafil) Interactions

Kelly Brown MD, MBA

Reviewed by Kelly Brown MD, MBA

Written by Geoffrey C. Whittaker

Published 04/22/2021

Updated 05/25/2024

Sildenafil (generic for brand-name Viagra®) is a safe and effective prescription medication for erectile dysfunction (ED) that can improve your sex life greatly. But there are risks to taking it incorrectly, including possible sildenafil interactions.

This phosphodiesterase type 5 enzyme (PDE5) inhibitor essentially works to sustain dilation and blood flow throughout the body and within your penis, resulting in better, firmer erections. However, taking sildenafil with certain other medications can be dangerous.

If you’re wondering how to safely combine Viagra and antibiotics or hydroxyzine and Viagra, consult a healthcare professional for guidance. But some medications should always be taken carefully — and some shouldn’t be taken together at all.

Below, we’ll go over possible Viagra interactions and why they pose serious risks and contraindications. We’ll also share some general tips on how to take sildenafil safely.

Generally speaking, sildenafil is safe and effective when used as directed. But like most medications, it can have some potentially harmful drug interactions when combined with the likes of nitrates, blood pressure medication, antifungals, and, yes, grapefruit juice.

If you mix these with sildenafil, you may see more intense side effects than usual, as well as some new adverse effects.

The most commonly reported adverse effects of PDE5 blockers like sildenafil are blood pressure complications (particularly when taken with alpha blockers).

Other common sildenafil side effects include:

  • Headache

  • Flushing

  • Dyspepsia

  • Abnormal or blurred vision (retinitis pigmentosa)

  • Nasal congestion

  • Back pain

  • Dizziness

Many of these will clear up over time for most users — but when taking other medications at the same time, serious problems could occur. 

There are some major drug interactions with Viagra. Sildenafil should never be combined with nitrates, blood pressure or hypertensive medications, alpha blockers, prostate medications, or other PDE5 inhibitors without the knowledge and guidance of a healthcare professional.

Taking sildenafil with other medications or supplements on this list could result in serious side effects. In extreme cases, this includes a very real risk of death.

Here are several ​​sildenafil drug interactions you definitely want to avoid.

1. PDE5 Inhibitors

Hey boys, no mix-and-match allowed with penis pills. You shouldn’t take sildenafil with other PDE5 inhibitors. Among other things, you could stop your own heart, so don’t take two ED drugs simultaneously.

This includes sildenafil (Revatio®, Viagra), tadalafil (Cialis®, Adcirca®), avanafil (Stendra®), and vardenafil (Levitra®, Staxyn®).

2. Nitrates

Unfortunately for those who want to double up on dick pills, Viagra and nitrates don’t mix. Nitrates can cause similar cardiovascular complications to other medications on this list when combined with PDE5s.

This includes nitroglycerin, butyl nitrate, isosorbide mononitrate, and street drugs called “poppers,” such as amyl nitrate or amyl nitrite. So if you’re taking nitrates, DO NOT take sildenafil or any of the other drugs mentioned.

3. Blood Pressure (Hypertension) Medications

Sildenafil citrate was once considered a blood pressure medication for people at risk for heart attack and those experiencing chest pain (angina).

Today, doubling up on pulmonary arterial hypertension (PAH) medications — like nitrate isosorbide dinitrate or the sGC stimulator riociguat — could result in lots of issues.

4. Alpha Blockers

Alpha blockers are another type of blood pressure medication that can cause sudden low blood pressure when mixed with ED meds like sildenafil. You definitely want to avoid mixing these.

If you’re currently using alpha blockers, give your healthcare provider a heads up before accepting a sildenafil prescription.

5. Prostate Medications

Medications like tamsulosin that treat conditions like benign prostatic hyperplasia (BPH) can have similar side effects like sudden drops in blood pressure. These can deepen when combined, making it a dangerous sildenafil drug interaction.

6. Antifungal Drugs

Certain antifungal drugs — like itraconazole, ketoconazole, erythromycin, clarithromycin, and doxazosin — can also increase the concentration of sildenafil in your blood. This could elevate your risk of common and more serious side effects.

So if you’re taking one of these, make sure to discuss dosage and safety with your healthcare provider. 

7. HIV Protease Inhibitors and Antibiotics

Some HIV medications — like ritonavir and antibiotics, such as Biaxin® — can increase the concentration of sildenafil in your bloodstream. Talk to your healthcare provider about potential risks if you’re on either type of medication.

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Medications and supplements present the most obvious sources of risk. But we’d also like to call your attention to the food and beverage side of risk factors. 

A handful of things you eat and drink could cause problematic interactions. We’ll touch on a few below.

Alcohol

Boozing with penis pills isn’t exactly dangerous in moderation, but it’s still not a great idea. According to FDA (U.S. Food and Drug Administration) data, alcohol consumption alongside PDE5 inhibitors can cause complications, including some nasty blood pressure drops.

We’re just gonna put this out there: Viagra and alcohol aren’t an amazing combination, so keep the drinking light.

Grapefruit and Grapefruit Juice

Most people know grapefruit to be a healthy citrus fruit, but for those taking PDE5 inhibitors, it can be problematic.

Grapefruit can increase concentrations of medication in your system. Combining Viagra or Cialis and grapefruit isn’t recommended, so maybe just have melon or berries with your breakfast instead.

High-Fat Foods

While it’s not exactly a side effect risk, eating high-fat meals before taking Viagra may have some undesired consequences. Specifically, it can delay the onset of the effects of Viagra.

A double cheeseburger isn’t one of the more important foods to avoid with Viagra. However, if you want to be ready to go around dessert time, you might want to skip the fries, ya know?

Choose your chew

There aren’t many ailments or illnesses that outright block you from using Viagra. But a number of medical conditions should absolutely be shared with your healthcare provider.

These include:

  • Sickle cell anemia

  • Irregular heartbeat

  • Previous instances of heart failure

  • Kidney disease

  • Leukemia

  • Liver disease

  • Peyronie’s disease

If you’re currently being treated or have been diagnosed with any of these, let a healthcare professional know before starting an ED prescription.

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To avoid dangerous interactions, risks, and other avoidable problems associated with sildenafil, we suggest learning how to take Viagra for the best results.

Mixing and matching medications could present life-threatening risks — and erectile dysfunction medications like Viagra are no exception. If you’re taking Viagra or want to take it, you’ll need to be careful to avoid serious contraindications that could put your health at risk.

Here’s how to safely approach a Viagra prescription (or any other ED drug):

  • Talk to a healthcare provider. Many factors can impact your chances for ED. The most common include obesity, heart disease, high blood pressure, depression, anxiety, illicit or prescription drug use, alcohol use, high cholesterol, diabetes, and performance anxiety. A clearer picture of what’s affecting you will help you find the right treatments.

  • Take sildenafil only as directed. Don’t use more than the recommended dosage of Viagra.

  • Don’t mix with “OTC Viagra.” Avoid mixing prescription sildenafil with so-called “over-the-counter Viagra” supplements you find in gas stations.

  • Know when to seek medical attention. Keep an eye out for four-hour erections (also known as priapism), which will need emergency attention. If you think you’re suffering from an allergic reaction or experience chest pain or other heart problems, seek medical advice immediately.

If you’re just learning about the treatment of erectile dysfunction, we have resources available to help you figure out if tadalafil or sildenafil is right for you.

Ready to get started? Our sexual health resources are just a click away — and safe for everyone.

4 Sources

  1. Dhaliwal A et al. (2023). PDE5 Inhibitors. https://www.ncbi.nlm.nih.gov/books/NBK549843/
  2. National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). (2017). Definition & Facts for erectile dysfunction. https://www.niddk.nih.gov/health-information/urologic-diseases/erectile-dysfunction/definition-facts
  3. Sooriyamoorthy T, et al. (2023) Erectile Dysfunction. https://www.ncbi.nlm.nih.gov/books/NBK562253/
  4. VIAGRA® (sildenafil citrate) tablets, for oral use . (n.d). https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/20895s039s042lbl.pdf.
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 is a founding member of Posterity Health where she is Medical Director and leads 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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