Sildenafil Side Effects: What To Look Out For

October 30, 2021

Since it was first approved by the Food and Drug Administration in 1998, sildenafil has been prescribed to millions of American men for erectile dysfunction. 

You’ve almost certainly heard of sildenafil before, although you're probably more familiar with the name Viagra®. Sildenafil is the active ingredient in Viagra, which has dominated the ED landscape for twenty years, becoming a household name in the few years after approval. It's still the most popular ED med prescribed in the U.S.

Sildenafil has a significant impact on your body, primarily by increasing your blood flow, which is why it requires a prescription from a licensed doctor to purchase.

While sildenafil/Viagra is considered safe for most men, it does have some known side effects, just like most medications, and it isn't a fit for everyone. 

What Effect Does Sildenafil Have On the Body? 

Once you know exactly what sildenafil does, it's easier to understand the potential side effects. 

Sildenafil is one of a class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. All of the prescription drugs used to manage erectile dysfunction belong to this class, including tadalafil (Cialis®) and vardenafil (Levitra®)

These drugs works by releasing the body's own "braking" mechanism on blood flow, allowing more blood to flow into the penis and facilitating an erection.

  1. When you experience mental or sensory sexual stimulation, you enter into a state of arousal.
  2. Once aroused, your brain and certain glands release chemical messages that travel throughout your body to prepare you for sexual activity. 
  3. One of these chemical messengers is a compound called nitric oxide. It helps to increase the production of cyclic guanosine monophosphate (cGMP), which basically tells your muscles to relax and your blood vessels to expand. These changes will increase the blood flow throughout your body, but especially to your penis in order to create an erection.
  4. PDE5 is an enzyme located in the walls of your blood vessels that regulates cGMP, reversing its effects and restoring your muscles and blood vessels to normal after an erection or ejaculation.
  5. Sildenafil or any of the other PDE5 inhibitors block this enzyme from performing its normal function to keep your blood vessels dilated, muscles relaxed, and erection firm. It is essentially over-riding the body's normal check-and-balance system on erections and blood flow.

PPDE5 inhibitors like Viagra, Cialis, and Levitra have been used by millions of men safely and effectively since approval over twenty years ago.


What Are the Possible Side Effects of Sildenafil?

Sildenafil is safe for most men, but for those with underlying medical conditions it can cause issues. 

The most significant impact that sildenafil has on your body is that it increases blood flow. As a result, you can experience a variety of minor side effects including:

  • Headaches
  • Stuffy or runny nose
  • Upset stomach
  • Diarrhea
  • Ringing in your ears
  • Nosebleeds
  • Prolonged erections
  • Sensitivity to light
  • Rash

Most of these side effects are uncommon and even rare. According to one four-year study on sildenafil, the most common side effects were headaches (28%), flushing (21%), dizziness (8%), abdominal pain (6%), and nasal congestion (5%). 

The most dangerous side effects of sildenafil are when it’s used in combination with other drugs. There is a long list of potential lethal interactions when sildenafil is mixed with other medications. It’s important that you tell your prescribing healthcare professional all of the other drugs that you're currently taking, especially if they have any effect on your blood. 

The most dangerous drug interactions involve nitrates and medications for high blood pressure and chest pain. Taking any of these drugs with sildenafil can result in dangerously low blood pressure that may require hospitalization due to dizziness, fainting, or even a heart attack or stroke. 

When using sildenafil, seek immediate medical help if you experience the following serious side effects, as they may be a sign of a medical emergency including an allergic reaction or cardiovascular distress:

  • Flushing in the face, neck, chest, and body
  • Nausea
  • Dizziness
  • Muscle pains
  • Chest pain (angina) or back pain
  • Blurred vision or vision loss
  • Sudden decrease in hearing or total hearing loss
  • Trouble breathing
  • Swelling of the lips, tongue, and/or throat

What To Do If You Experience Side Effects 

It’s generally unlikely that you will encounter any lasting side effects when taking sildenafil, but it is a possibility. The good news is that these effects should only last as long as the drug is in your system. 

While the drug can technically stay in your system for as many as 24 hours, the effects are usually diminished by the fifth hour. It might not even take that long depending on your age, metabolism, and your dose. 

Drinking more water can help your body to speed up its filtration of your blood and get the drug out of your system faster, too. 

Sildenafil does not negatively interact with most over-the-counter medications, so you may be able to seek relief that way if a minor symptom is bothering you. For example, if you're experiencing a headache, muscle ache, or other pain, using ibuprofen or acetaminophen should be fine. For an upset stomach, indigestion, nausea, or diarrhea, it shouldn't be an issue to take over the counter stomach medicines. 

If you're concerned or have questions, ask your doctor about your side effects first.

Can You Prevent Side Effects From Happening? 

There isn’t much that you can do to prevent side effects from happening, but you may be able to reduce their severity. Talk to your doctor about reducing your sildenafil dose. 

The most commonly prescribed dose of sildenafil is 50 mg, but your doctor may prescribe the maximum dose of 100 mg if lower doses aren’t cutting it. If you're taking either of these doses, talk to your doctor about lowering your dose to 25 milligrams. It’s possible that this reduction may reduce or eliminate any side effects that you may have been experiencing. 

Another option is to eat a light meal before taking sildenafil. For best results, however, it’s recommended to take sildenafil on an empty stomach. While that may sound counterintuitive, there likely won’t be a significant change to the quality of your erection. 

The Takeaway 

Several side effects have been associated with taking sildenafil, but they're seen in a minority of cases. Most guys who take medications that might interact with sildenafil will be warned by their prescribing physician ahead of time, and if sildenafil is unsafe due to existing medical conditions, the doctor likely won't prescribe sildenafil in the first place.

The most important thing is to be transparent with your prescribing clinician.

Sildenafil is not suitable for many men with high blood pressure or cardiovascular conditions, so make sure to speak with a doctor before using.

In the event that you do experience minor side effects like flushing, they should diminish within hours as the drug exits your system.

Curious if ED meds are right for you? Find out the easy way with an online consult from Rex MD. It's fast, and our meds are delivered to your door (if prescribed) at industry-leading prices. Click here to start your consult.



FDA approves Viagra |

Phosphodiesterase-5 (PDE5) Inhibitors In the Management of Erectile Dysfunction | NCBI

The physiology of sexual arousal in the human female: a recreational and procreational synthesis. | PubMed

The role of nitric oxide in penile erection | PubMed

Cyclic guanosine monophosphate mediates penile erection in the rat | PubMed

Four-Year Review of Sildenafil Citrate. | NCBI

Sildenafil (Oral Route) Side Effects | Mayo Clinic

How Long Does Viagra Last & Stay in Your System? | MedExpress

Sildenafil citrate 100 mg starting dose in men with erectile dysfunction in an international, double-blind, placebo-controlled study: effect on the sexual experience and reducing feelings of anxiety about the next intercourse attempt | PubMed

Do food and dose timing affect the efficacy of sildenafil? A randomized placebo-controlled study | PubMed

Back to list

Disclaimer : This article is for information only and should not be considered medical advice. Always speak with your doctor about your health and the benefits or risks of any treatment or intervention. This information should not be relied on as a substitute for professional medical advice.