Is Sildenafil Safe for Erectile Dysfunction (ED)?

In the ‘90s, researchers set out to test a medication called sildenafil citrate for treating high blood pressure and angina (chest pain) from heart disease. While the treatment appeared promising for these purposes, it proved to be more potent in — ahem — another more sensitive area of the body. 

Many of the male participants were embarrassed to disclose to the research staff that they were experiencing erections with no sexual stimulation during the trial.

While sildenafil was intended to relax and dilate blood vessels around the heart, it was also active in the blood vessels around the penis. That meant it increased blood flow around the heart and also to the genitals, hence the erections. Talk about getting more than you bargained for.

Needless to say, researchers took an unexpected pivot and decided to investigate sildenafil as a treatment for erectile dysfunction (ED). After all, if it was causing erections among men who weren’t necessarily looking for that effect, imagine what it could do for men who were struggling to stay hard.

After further trials, sildenafil citrate was approved by the Food and Drug Administration (FDA) as the active ingredient in brand name Viagra®, now a very well-known drug for ED.

For most men, sildenafil is a safe and effective treatment for ED when used as prescribed. However, like all drugs, it comes with its own set of potential side effects and interactions. 

We’ve broken down how sildenafil works for treating ED, who shouldn’t use it and how to ensure that you’re using it safely to improve your sex life.

How Does Sildenafil Treat ED?

Thanks to the unintended discovery during those heart disease trials, we now have a good understanding of all the ways sildenafil works in the body.

Treating ED is the most prevalent and well-understood of uses for Viagra  — it’s also used in different dosages for treating pulmonary arterial hypertension under the brand name Revatio®. So, how does it work anyway? 

Sildenafil falls into a class of drugs called PDE5 inhibitors, along with other drugs like Cialis® (tadalafil), Stendra® (avanafil) and Levitra® (vardenafil). These are the gold standard drugs for the treatment of erectile dysfunction. In fact, studies show that just one dose of Viagra has a 70 to 80 percent success rate for treating ED. 

PDE5 stands for phosphodiesterase 5, an enzyme that plays an important role in regulating blood flow to many parts of your body, including the soft erectile tissue inside your penis. 

Specifically, PDE5 can keep the smooth muscle in your penis from relaxing, which can prevent blood flow. PDE5 inhibitors increase blood flow to your penis, resulting in longer, harder erections when you’re sexually aroused.

Your next question is probably when it will start working and how long sildenafil lasts. And we get it. This is important stuff when you’re planning the logistics of your evening. 

Most of the time, Viagra begins to work within 30 to 60 minutes of taking it. 

It may work faster if you take it on an empty stomach, since it reaches your digestive tract sooner this way. It may work more slowly if you take it after eating a meal, especially one that contains more fat. So make sure that you strategically pop that little blue pill based on what your plans are.

As for how long it lasts, the packaging insert says Viagra has a half-life of four hours.

No, this doesn’t mean you’re still going to have a hard-on at that point. It just means that the drug will still be in your system, but not at a high enough concentration to have noticeable effects. For the best results, plan to have sex within these first four hours of taking sildenafil.

Get hard, stay hard

Get effective, affordable ED treatment... from your home!

Is Sildenafil Safe?

When used as directed to treat erectile dysfunction, sildenafil is safe and effective for most men. However, like any drug, it has potential side effects and drug interactions that are important to consider before using. 

The most common sildenafil side effects include: 

  • Headaches, which affect up to 28 percent of men who use it

  • Muscle aches and back pain

  • Stuffy nose, due to its dilating effects on blood vessels

  • Lightheadedness or dizziness

  • Flushing of the skin on your cheeks

  • Heartburn or indigestion, because of how sildenafil acts on the smooth muscle cells throughout your body

  • Nausea, though this is only reported by a small percentage of men who use it

  • Reduced blood pressure

  • Blurred vision or otherwise abnormal vision, though this is usually mild and temporary

If you take a dose of sildenafil above 100mg, you’ll have a higher risk of experiencing any of these side effects.

Other more serious but less common side effects of Viagra have also been reported, such as:

  • Priapism, or a prolonged erection that lasts several hours and can become painful

  • Sudden hearing loss, called sensorineural hearing loss (SSHL), which involves damage to the inner ear 

  • Rare permanent loss of vision due to optic nerve damage

If you experience any of these potentially serious side effects, seek immediate medical attention. Your healthcare provider will be able to help you figure out whether they are likely to be temporary or more serious. If the side effects are serious or even if they just impact your life too much, they may recommend an alternative drug or another ED treatment. 

Is Sildenafil Hard on the Heart?

Sildenafil acts on the blood vessels in your penis, so you may wonder whether it has any worrisome effects on your cardiovascular system as a whole.

There have been reports of stroke, heart attack and irregular heartbeats among some people who take Viagra. However, there is currently no solid evidence that directly links sildenafil or other ED medications to heart attacks in men. 

The fact is that people who have ED are at a higher risk of having heart disease — and vice versa. For example, problems with both your penis and your heart can be associated with a vascular condition that affects blood flow. 

PDE5 inhibitors like sildenafil may not be safe for people who have existing heart problems. It’s contraindicated among people who have had a heart attack, stroke or irregular heartbeat within the last six months, as well as people who have abnormal blood pressure at rest or a history of heart failure or unstable angina.

A heart attack occurs when the supply of blood to the heart is abruptly blocked. It’s usually caused by coronary artery disease — a form of heart disease that involves the buildup of plaque inside the walls of the arteries that supply blood to your heart.

As a vasodilator, sildenafil actually increases blood flow throughout your body, including to areas other than your penis. By doing so, it also lowers blood pressure. This drop is generally so small that most men don’t notice it, even ones who are taking medication for high blood pressure.

Still, it can be dangerous — even life-threatening — if you have existing heart-related concerns. 

Additionally, sildenafil can interact with drugs called nitrates, which are commonly prescribed for heart-related conditions. We’ll discuss this more next. 

Finally, sexual activity of any type can put a strain on your heart. If you have an existing heart condition, the physical stress of having sex may increase your risk of heart attack, stroke or other cardiovascular events.

ED treatments, delivered

No matter the treatment plan, the best place to start is somewhere.

New

Hard Mints by Hims

Combination Chewable Treatment

From £3/use

These mint-flavored chewables are packaged in a discreet portable tin. Our personalised treatments contain active ingredients used to treat ED at different dosages to meet your specific needs.

Traditional Pill

SildenafilGeneric Viagra®

From £2.25/use

The most commonly prescribed ED treatment, contains the same active ingredient as Viagra® but is 80% more affordable than the brand name.

New

Hard Mints by Hims

Daily Chewable Treatment

From £26/month

These mint-flavored once-daily chewables are packaged in a discreet portable tin. Our personalised treatments contain active ingredients used to treat ED at different dosages.

Traditional Pill

Daily TadalafilDaily Generic Cialis®

From £21/month

A clinically proven treatment for erectile dysfunction that helps men achieve and maintain erections more easily. It gives you the freedom to enjoy spontaneous sex without needing to plan ahead.

Traditional Pill

As-Needed TadalafilGeneric Cialis®

From £2.25/use

The unbranded, more affordable generic form of Cialis® taken as needed. It is clinically proven to help men get and keep harder erections for up to 36 hours.

Traditional Pill

Viagra Connect®

From £5.83/use

The over-the-counter branded version of sildenafil. Viagra Connect® improves blood flow to the penis, helping you achieve and maintain strong and satisfying erections.

Important safety information for Sildenafil, Tadalafil, Tadalafil Daily or Viagra Connect.

Who Should Avoid Sildenafil?

There are certain types of medications that shouldn’t be taken with sildenafil due to potentially serious interactions, like:

  • Nitrates (e.g., nitroglycerin, isosorbide dinitrate or isosorbide mononitrate) used to treat congestive heart failure and manage high blood pressure

  • Alpha-blockers, which relax blood vessels and are prescribed for hypertension and benign prostatic hyperplasia (BPH), a common prostate condition among aging men that can lead to enlarged prostate and urinary symptoms

  • Recreational drugs called “poppers,” which may contain amyl nitrite

  • Ketoconazole, a drug used to treat certain fungal infections

When nitrate-containing drugs, poppers or alpha-blockers are used with sildenafil, they can cause a sudden and severe drop in your blood pressure. This may make you feel dizzy or, more seriously, could cause you to pass out.

Ketoconazole can block or overstimulate certain proteins in your liver that break down sildenafil. This can result in higher-than-normal levels of sildenafil in your body, which may lead to headaches, flushing and dizziness.

Sildenafil can even trigger a heart attack or stroke when combined with certain other medications. 

The best way to avoid adverse effects is to disclose all of your prescription, over-the-counter and recreational drug use to your healthcare provider before you begin using Viagra. 

Additionally, certain pre-existing medical conditions may increase your risk of experiencing side effects from using sildenafil. 

For instance, inform your healthcare professional if you have: 

  • A deformed penis shape or condition called Peyronie’s disease, in which the penis is curved

  • Heart issues like angina, narrowing of the aortic valve, irregular heartbeat or heart failure, or have previously had a stroke or heart attack

  • Blood cell-related conditions, such as multiple myeloma, sickle cell anemia or leukemia

  • High blood pressure, low blood pressure or high blood pressure in the blood vessels supplying your lungs (a condition called pulmonary arterial hypertension, or PAH)

  • An eye-related condition, such as retinitis pigmentosa (a condition in which the cells of your retina break down over time), which can increase your risk of other vision problems when using ED medications

  • Bleeding problems or stomach ulcers

  • Liver and kidney problems, including being on dialysis

How to Use Sildenafil Safely

When you’re dealing with ED, it can understandably trigger a range of emotions. Frustration, anxiety, depression and shame can creep into more than just your bedroom, impacting your everyday quality of life.

It may even feel tempting to throw caution to the wind and try anything just to get some sense of control back. However, it’s critical to evaluate the situation and understand your options.

Sildenafil is highly effective and safe when used as directed, but that doesn’t mean you should disregard potential risks. 

To reduce your risk of side effects and interactions, make sure you adhere to the following tips for how to take Viagra for the best results

  • Take it as prescribed. Sildenafil is most commonly prescribed to be taken one time per day in doses between 25 and 100mg. Your healthcare provider will determine the best dosage for you based on a number of factors. More does not equal better, and it’s important to stick to your prescription. 

  • Use it strategically. Sildenafil is most effective when taken approximately one hour before sex. For most people, it can provide ED relief for around four hours before it begins to decrease in the body. Take this into account when you’re planning to use sildenafil for sex. 

  • Know the potential side effects of sildenafil. Sildenafil isn’t for everyone. It can interact with certain medications, like nitrates, and put your health at risk. It may also lead to side effects for some men, like dizziness, prolonged erection, or visual changes. 

  • Communicate with your provider. We know how awkward it can be to talk about your sexual activity with, well, most people, but especially someone you may not see very often. It’s important to make sure your healthcare provider is aware of any preexisting health conditions you have, as well as any supplements or over-the-counter, prescription and recreational drugs you use.

If you’re unsure how to take sildenafil properly or whether it’s even right for you, consider speaking to one of our many health professionals available to provide medical advice. 

Shop by treatment options

No matter the treatment plan, the best place to start is somewhere. Early action is the best hair loss prevention.

No-pill option

Hair Hybrids by Hims

The Combination Hair Loss Spray

From £26/month

This spray treatment combines two active ingredients used for treating hair loss and hair regrowth.

Important Safety Information

No-pill option

Hair Hybrids by Hims

The Combination Hair Loss Serum

From £26/month

This serum treatment combines two active ingredients used for treating hair loss and hair regrowth.

Important Safety Information

Generic Treatment

Finasteride & Minoxidil Combo Kit

From £30/month

This combo kit includes two treatments. The once-daily tablet is clinically proven to stop hair loss. The alcohol-free topical serum, applied twice daily, is used for hair regrowth.

Important Safety Information

Generic Treatment

Finasteride

From £23/month

This once-daily tablet is clinically proven to stop hair loss.

Important Safety Information

Hair Hybrids by Hims

Alcohol-free Minoxidil Serum

From £21/month

This alcohol-free topical serum, applied twice daily, is used for hair regrowth

Important Safety Information

Is Sildenafil Safe? The Bottom Line

Yes, sildenafil is usually a safe and effective drug for ED management when it’s taken as prescribed. Just keep the following things in mind if you’re considering using it to improve your sex life. 

  • Understand potential side effects. Viagra can cause side effects, interact with certain medications and be a bad option for people with certain health conditions. Speak openly with your healthcare provider about your lifestyle, existing conditions, and other drug use before starting Viagra, or any other erectile dysfunction medications.

  • Know there are other options. In some cases, another ED drug — such as Cialis or its generic tadalafil, and Stendra or its generic avanafil — may be a better fit for you. Alternatively, you might be interested in our hard mints, which are chewable ED medications that contain the same active ingredients as other ED prescriptions, but in personalized dosages.

  • Identify other factors that may be causing your ED. ED affects an estimated 30 to 50 million men in the United States alone. It’s a multifactorial condition and many men experience psychological ED. This is when things like depression, anxiety or sexual performance anxiety get in the way of your erection. And it’s more than mind over matter — these are real issues that require real attention.

ED is a cock block for everyone involved. Fortunately, living with ED doesn’t need to be a life sentence, nor is it uncommon. 

If you’re ready to pursue a solution and gain back confidence in the bedroom, check out our online therapy support or take our free quiz to help you navigate next steps.

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 or medication.

ED treatment that comes to you

Answer some questions

Consult with a licensed provider

Get ED pills delivered, if prescribed

Get started