Viagra (Sildenafil) Interactions

Kristin Hall, FNP

Reviewed by Kristin Hall, FNP

Written by Geoffrey Whittaker

Published 04/22/2021

Updated 08/17/2023

When it comes to your penis, you want to avoid cutting corners on things that have to do with safety. Luckily, sildenafil (the generic version of brand-name Viagra®) is a safe and effective prescription medication for erectile dysfunction (ED). 

Yes, it can improve your sex life greatly if you’re suffering from ED. 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. 

It’s a great option for men who need a little help in the sexual activity department. But you should be aware of the risks associated with playing mix and match because taking sildenafil alongside other medications can be dangerous. 

Below, we’ll go over the serious risks and contraindications you’ll want to avoid at all costs. We’ll also share some general tips on how to take sildenafil safely to protect your penis (and your life).

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Sildenafil Interactions and Adverse Effects

Generally speaking, sildenafil is safe and effective when used as directed. But like most medications, it can have some potentially harmful drug interactions. 

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

Common sildenafil side effects like headache, flushing, dyspepsia, abnormal or blurred vision, nasal congestion, back pain, myalgia, nausea, dizziness and rash can occur. Many of these will clear up over time for most users. 

However, major interactions can cause far more serious issues. Take a look at what we mean below.

Major Viagra Drug Interactions

There are some major drug interactions you’ll want to avoid at all costs. Taking sildenafil with other medications and supplements on this list could result in serious side effects. In extreme cases, this includes a very real risk of death.

  • PDE5 inhibitors. Hey boys, no mix-and-match allowed with penis pills. You should not take sildenafil alongside 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®), among others.

  • Nitrates. Unfortunately for those who want to double up on the dick pills, Viagra and nitrates don’t mix. Nitrates can cause similar cardiovascular complications to other medications on this list when mixed with PDE5s. This includes nitroglycerin, butyl nitrate 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.

  • Blood pressure medications. Remember, sildenafil citrate was once considered a blood pressure medication for people at risk for heart attack (angina). Even though it’s a penis pill for the most part today, doubling up on blood medications — like nitrate isosorbide dinitrate or the sGC stimulator riociguat — could result in lots of issues. Commonly reported side effects included mild issues like indigestion, back pain, headache, muscle pain, flushing, stuffy nose and abnormal vision. Stop the medication immediately and seek emergency assistance if your blood pressure drops suddenly or if you experience vision loss.

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

Moderate Sildenafil Interactions

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 — and the medications that wouldn’t seem to have much to do with your heart or penis. 

A number of things you eat and drink could cause problematic interactions, as could other medications.

  • Alcohol. Boozing with penis pills isn’t exactly dangerous in moderation, but it’s still not a great idea. According to FDA 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. 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 is not recommended, so maybe just have melon or berries with your breakfast instead. 

  • Antifungal drugs. Certain antifungal drugs like ketoconazole, erythromycin, clarithromycin and doxazosin can also increase the concentration of sildenafil in your blood. This could elevate your risk of both common and serious side effects. So if you’re taking one of these, make sure to discuss dosage and safety with your healthcare provider. 

  • 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 your risks if you’re on either type of medication.

Minor Viagra Interactions

While it’s not exactly a side effect risk, eating high-fat meals before taking Viagra can 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 — but if you want to be ready to go around dessert time, you might want to skip the fries, ya know?

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Health Condition Interactions With Viagra

There aren’t many health conditions that outright block you from using Viagra, but a number of conditions will need to 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, be sure to let your healthcare professional know before starting an ED prescription.

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Sildenafil Interactions: How to Stay Safe

We probably don’t need to tell you this, but you can’t go taking five Viagra pills and hope for some sort of Hulk-esque super-erection. Nobody’s gonna turn green and become unstoppable, and the only thing you’ll be smashing is the 911 shortcut on your smartphone.

Sure, your penis might turn other colors — but not for a good reason.

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

Here’s what to remember:

  • Take sildenafil only as directed.

  • Familiarize yourself with the most common side effects of sildenafil, and know what to do if you see them.

  • Don’t use more than the recommended dosage of Viagra.

  • Keep an eye out for four-hour erections (also known as priapism), which will need emergency attention. 

  • Avoid mixing prescription sildenafil with so-called “over-the-counter Viagra” supplements you find in gas stations.

  • If you think you’re suffering from an allergic reaction or experience chest pain or other heart problems, seek medical advice immediately.

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Viagra Drug Interactions: Final Thoughts

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.

Before you take Viagra, know the following information inside and out:

  • Erectile dysfunction is a common condition. The National Institutes of Health estimates 30 million men nationwide experience some degree of ED. 

  • While erectile dysfunction treatments like tadalafil (generic for Cialis) and avanafil (generic for Stendra) may work differently, many of them present the same risks as sildenafil.

  • 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, high cholesterol, diabetes and performance anxiety. The medications to treat these can also cause unforeseen problems.

  • Before you take Viagra or medications like our chewable ED meds hard mints, talk to your healthcare provider about other medications you’re taking.

  • Your healthcare provider will also go over potential risks associated with your diet, drinking habits and lifestyle choices.

If you’re just learning about the treatment of erectile dysfunction, we have resources available to help you determine 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. Sooriyamoorthy T, Leslie SW. Erectile Dysfunction. [Updated 2023 May 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:
  2. U.S. Department of Health and Human Services. (n.d.-a). Definition & Facts for erectile dysfunction - NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases.
  3. HIGHLIGHTS OF PRESCRIBING INFORMATION: VIAGRA® (sildenafil citrate) tablets, for oral use . (n.d.-b).
  4. Dhaliwal A, Gupta M. PDE5 Inhibitors. [Updated 2023 Apr 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:
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.

Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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