Common Sildenafil Interactions

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 4/23/2021

When it comes to penis pills, sildenafil is the original, the alpha, the first on the scene. Sildenafil is the generic of Viagra®: the first celebrity pill in the world of erections. 

If you’re reading this, you’re probably investigating sildenafil as an option for a problem, or a “maybe” problem, or a hypothetical problem. The question we always see: does sildenafil really work?

Well, yes. Sildenafil is a safe and effective prescription medication for erectile dysfunction, and it can improve your (or anyone else’s) sex life greatly if there are arousal issues at plan—if it’s employed to treat the right problem.

In other words, the pill is great for treating many types of ED. To understand how Sildenafil works, you need to first understand how your penis works. 

Erections and Erectile Dysfunction

Erections occur when blood flow to the penis’s blood vessels increases, and the blood becomes trapped in two long chambers called the corpora cavernosa. 

When you get turned on, your brain sends chemical communications to those blood vessels saying “dilate, right now,” and they do what they’re told, so that blood flows in. It becomes trapped there, and that’s what keeps you erect. 

So as you might suspect, erectile dysfunction is the condition you have when something’s going wrong in those processes. 

Of the many factors that can impact your chances for ED, here are some of the most common: obesity, heart disease, high blood pressure, depression, anxiety, illicit or prescription drug use, alcohol, high cholesterol, diabetes and performance anxiety.

Perhaps because that list is so long, ED is a common condition; the National Institutes of Health estimates 30 million men nationwide experience some degree of ED. 

The NIH, by the way, defines erectile dysfunction as a “condition in which you are unable to get or keep an erection firm enough for satisfactory sexual intercourse,” which means you have ED whether your erection is incomplete OR a non-starter. No partial credit, guys. 

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What Is Sildenafil?

Put simply, sildenafil is the OG prescription ED treatment. The generic version of Viagra, sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor, which essentially works to sustain dilation and blood flow within your penis, resulting in better, firmer erections. 

Unlike tadalafil (Cialis®) for instance, which can work for a day or more, sildenafil is a sort of pre-game solution to the problem, like carbo loading for your erections. It’s best taken when the action is going to take place within a few (up to 4) hours, according to the National Library of Medicine.

It’s a great option for men with ED, and about 70 percent of men respond well to PDE5 inhibitors, according to Harvard Medical School. But it’s largely dependent on your causes. The best results come for men with “no identifiable organic cause”—they see approximately a 90 percent success rate. 

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Sildenafil Side Effects and Drug Interactions

Like most medications, sildenafil can have some potentially negative drug interactions. The most commonly reported for PDE5 blockers like sildenafil are complications related to blood pressure (particularly when taken with alpha blockers). 

PDE5s, because of how they interact with blood vessels, can be used to treat hypertension, which sounds like a double benefit but is actually the main reason it’s important to disclose other medications before taking sildenafil. 

Doubling up on the blood medications could result in a lot of issues, particularly if you have high blood pressure.

Commonly reported side effects included mild issues like indigestion, back pain, headache, muscle pain, flushing, stuffy nose or abnormal vision. Stop the medication immediately and seek emergency assistance if your vision becomes abnormal.

You should not take sildenafil alongside other PDE5 inhibitors—it can cause really inconvenient problems, like death. Seriously, this is how you could stop your own heart. Don’t take two ED drugs simultaneously. And if you’re taking any other blood pressure meds, talk to your healthcare provider before starting sildenafil. This includes PDE5s inhibitors, as well as alpha-blockers and antihypertensive medications. 

According to additional FDA data, alcohol consumption alongside PDE5 inhibitors can cause complications. And if you’re taking nitrates, DO NOT take sildenafil or any of these drugs.

There are also some rare side effects to be on the lookout for, that do occasionally happen. They include renal impairment, sudden hearing loss, and priapism (prolonged erection). According to the FDA, “If priapism is not treated immediately, penile tissue damage and permanent loss of potency could result.” If your erection lasts more than four hours, get medical assistance.

Our blog also covers if you can take Viagra with blood thinners.

How You Take Sildenafil Matters

We probably don’t need to tell you this, but you can’t go taking five of these and hoping for some sort of Hulk-esque super erection. Nobody’s going to turn green and become unstoppable, get it? It’ll quite possibly turn other colors and become non-functional.

Once taken, sildenafil takes between 30 to 60 minutes to activate, and lasts for around four hours.

According to the FDA, doses range between 25mg and 100 mg, and those should be taken as needed ahead of planned performance. As much as sildenafil is a great option for giving you some control of your love life, if your sex life is unpredictable, you may be better served with a daily option, like tadalafil.

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Other Considerations

As much as ED might seem like a problem solved, there’s no guarantee sildenafil is going to be your magic pill, particularly if the cause of your particular ED isn’t physiological. It’s hard to do, but you might want to take a moment in addressing this problem to ask yourself whether something else might be at play—something psychological. 

Anxiety and depression can play a role in creating performance issues, and if you think this might be your problem go ahead and consult a healthcare professional, but consider asking for a referral to a psychiatrist or mental health professional, to examine other treatment options. Sildenafil might be one of several tools that end up making a more complex solution to your particular problem with ED.

If you’re just learning about ED, we have resources available to help you determine if either tadalafil (Cialis) or sildenafil (Viagra) are right for you. 

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.