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Feb 11, 2022
3 min read

Viagra side effects: what to expect, warnings and interactions

Viagra, and its generic counterpart, sildenafil, are effective treatments for erectile dysfunction (ED). Like all drugs, it also has the potential for side effects, ranging from mild to severe, and dangerous drug interactions.


If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.

Viagra is a popular and effective oral medication for treating erectile dysfunction (ED), or the inability to get or maintain an erection sufficient for a satisfying sex life.

Because ED is so common—affecting more than 30 million American men—there are quite a few drugs on the market formulated to help lessen its symptoms (Sooriyamoorthy, 2021). One of these drugs is Viagra. And like all drugs, it also comes with the potential for side effects, ranging from mild to severe, and can interact with some other medications. 

Here’s what to expect and where you should exercise caution before taking Viagra.

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Viagra side effects

Viagra, and its generic counterpart sildenafil citrate (see Important Safety Information), is an erectile dysfunction medication known as a PDE5 inhibitor that helps more blood flow to the penis. But, Viagra is not a magic pill. You don’t automatically get an erection just by taking it. You need sexual stimulation for it to work. And, there’s always the risk of some side effects. 

Here are the most common side effects of Viagra and some more serious (but uncommon) side effects to watch out for.

Common side effects

The most common side effects of erectile dysfunction medications include (Smith, 2021):

  • Flushing
  • Upset stomach, heartburn, or indigestion
  • Headache
  • Sensitivity to light (objects may seem to have a blue tinge)
  • Runny nose or nasal congestion
  • Body aches, including back pain
  • Temporary color vision changes

Serious side effects

Uncommonly, people may experience serious side effects while taking Viagra, including (Smith, 2021):

  • Chest pain
  • Shortness of breath
  • Severe headaches
  • Fainting
  • Erections that last longer than four hours (priapism)
  • Visual changes (like loss of sight)

If you notice any severe or prolonged symptoms at all, seek medical advice immediately.

Viagra warnings

People with certain medical conditions may need to exercise caution when taking PDE5 inhibitors like Viagra. 

Viagra can cause a drop in your blood pressure, usually within 1–2 hours after taking it. But it doesn’t happen to everyone. However, if you have low blood pressure, a history of heart attack or heart disease, or other medical issues, talk with your healthcare professional about whether taking sildenafil is safe for you (DailyMed, 2022).

Similarly, certain eye conditions like retinitis pigmentosa may increase the likelihood of adverse effects with Viagra, so check with your healthcare provider before using this drug. Viagra may also increase your risk of non-arteritic ischemic optic neuropathy (NAION) in some people––this is an eye problem that can lead to permanent vision loss (Smith, 2021).

Viagra drug interactions

Before you start Viagra, talk to your healthcare provider about other medications you are taking—both over-the-counter and prescription drugs. Some medicines may increase your risk of side effects if you take them with Viagra might cause adverse reactions when taken with other prescription and non-prescription medications.

You should not take Viagra if you are also taking nitrates, which includes prescription medications for chest pain (like nitroglycerin) and the recreational drug amyl nitrite (also known as “poppers”). The combination of nitrates and Viagra can lead to a dangerous (and potentially fatal) drop in blood pressure (Smith, 2021). 

Drugs that affect how your body breaks down Viagra may allow it to stick around longer, increasing the chance of side effects. For instance, the drugs called CYP3A4 inhibitors prevent your liver from getting rid of Viagra. Examples of CYP34A inhibitors include (DailyMed, 2022):

  • Ritonavir
  • Saquinavir
  • Erythromycin
  • Antifungals (like ketoconazole and itraconazole) 

Since one of the side effects of taking Viagra is lower blood pressure, people who take medications to lower high blood pressure (antihypertensives) may find that their blood pressure drops too low if they are also using Viagra.  

Alpha-blockers are drugs used to treat high blood pressure (doxazosin) and prostate issues (tamsulosin) like benign prostatic hyperplasia. This drug class is notorious for causing low blood pressure if taken with Viagra.

Similarly, if you combine Viagra with other PDE5 inhibitors (like Revatio [see Important Safety Information] for pulmonary hypertension) or other ED drugs like Cialis (generic name tadalafil; see Important Safety Information) or Levitra (generic name vardenafil), you again run the risk of a dangerous drop in blood pressure (DailyMed, 2021). 

Overall, Viagra is a safe and effective treatment for erectile dysfunction. Talk to your healthcare provider about your medical history and concerns, including side effects and potential drug interactions.


  1. DailyMed. (2021). Viagra- sildenafil citrate tablet, film-coated. Retrieved on Jan. 17, 2021 from
  2. Smith, B. P. & Babos, M. (2021). Sildenafil. [Updated Jun 29, 2021]. In: StatPearls [Internet]. Retrieved from
  3. Sooriyamoorthy, T. & Leslie, S. W. (2021). Erectile dysfunction. [Updated Aug 12, 2021]. In: StatPearls [Internet]. Retrieved from