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Erectile Dysfunction (ED) Medications: Types & How They Work

Kelly Brown MD, MBA

Reviewed by Kelly Brown MD, MBA

Written by Geoffrey C. Whittaker

Published 09/14/2017

Updated 04/14/2024

Whether you’re one of the 30 million men who have erectile dysfunction (ED) or not, you’ve almost certainly heard of Viagra®. Maybe you even know about other erectile dysfunction medications, like Levitra® or Stendra® or Cialis®, too. 

Understanding how they work is a whole different ball game, but it’s not complicated. Essentially, ED pills help relax certain muscles and boost blood flow to the penis — making it easier to get and stay hard during sexual activity. 

Below, we dig into the details to fully answer questions like “how do ED pills work?” and “what are the side effects of ED meds?” We also explain how quickly they work, how long they last and why supplements and other over-the-counter options probably won’t cut it.

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The U.S. Food and Drug Administration (FDA) has approved several medications for the treatment of erectile dysfunction, including:

  • Sildenafil (the active ingredient in Viagra or generic versions of Viagra)

  • Tadalafil (the active ingredient in Cialis)

  • Avanafil (the active ingredient in Stendra)

  • Vardenafil (the active ingredient in Levitra and Staxyn®) 

If you think you might have erectile dysfunction, learning about these medications is a good place to start. 

Currently, these FDA-approved ED medications are prescription medications — meaning they can’t be bought over the counter. 

Doctors often prescribe oral medications, aka sex pills, as a first line of defense. But chewable ED meds like our hard mints provide a fresh and convenient solution, and they contain the same active ingredients in Viagra and Cialis.

These ED drugs belong to a class of medications called PDE5 inhibitors, short for phosphodiesterase type 5 inhibitors. They suppress PDE5 (an enzyme in the smooth muscle cells of your blood vessels) so your blood vessels widen. This can increase blood flow to the tissue inside your penis, making it easier to get an erection after sexual stimulation.

There’s a reason sildenafil, tadalafil and other PDE5 inhibitors are some of the most common ED treatments — they work. In fact, these treatments can fully reverse erectile dysfunction in some cases. 

The Research Behind ED Pills

Tadalafil, for example, significantly enhanced erectile function as well as sexual activity in men of different ages throughout clinical trials.

From the newer generation of ED drugs, avanafil has shown to be just as effective at improving erectile function as older medications like sildenafil, tadalafil and vardenafil.

As to why Viagra is arguably the most popular ED medication? 82 percent of those taking a 100-milligram (mg) dosage saw improvement in their erections.

On top of working effectively, these are some of the safest ED drugs, thanks to ongoing testing and approval by the FDA. That said, there’s still a chance of experiencing side effects and risks (that come with taking any medication, really). We’ll get into that below.

Choose your chew

Add a boost to your sex life with our new chewable formats

Though erectile dysfunction pills work at different speeds based on their ingredients, most sexual dysfunction drugs take 30 to 60 minutes to start working with sexual stimulation.

For example, experts recommend taking Viagra one hour before sexual activity because it can take between 30 and 60 minutes for the medication to reach its highest concentration.

Cialis, on the other hand, reaches peak concentration anywhere between 30 minutes and six hours after taking it. So you’d want to take that one two hours before sexual activity.

After something faster? The newer medication avanafil ( brand-name Stendra) works the fastest — between 15 and 30 minutes. 

Regardless of the specific medication you use, it’s best to take your ED medication about an hour before you plan to have sex. Prepare ahead of time, and you’ll experience the medication’s full effects when you and your partner become intimate.

Comparing, FDA-Approved ED Treatments to Supplements

Avanafil is the only fast-working FDA-tested and approved ED drug, despite the fast-acting male enhancements being pushed these days. 

When it comes to those herbal or dietary supplements you see at gas stations or on sketchy websites, we’d pass.

While we often associate the words “herbal” and “natural” as being harmless or even better for us, these over-the-counter products may even contain counterfeit or unproven ingredients that aren’t safe or effective.

Learn more about why OTC ED drugs are risky in our article.

Choose your chew

To understand how long an ED medication will last, you need to know its half-life — which measures how long it takes for the concentration of the medication in your body to fall to half of its peak. 

The half-life of a medication determines how long it’ll remain active in the body.

Here’s a list of both the half-lives and duration of action for four of the most common ED drugs (PDE5 inhibitors):

  • Viagra (or sildenafil) lasts three to five hours after it’s consumed.

  • Cialis (tadalafil) has a half-life of 17.5 hours, meaning this drug lasts up to 36 hours after it’s consumed.

  • Levitra (vardenafil) has a half-life of four to five hours and remains active in the body for up to six hours after it’s consumed.

  • Stendra (or avanafil) has a half-life of three to five hours and remains active in the body for up to six hours after it’s consumed.

As you can see, vardenafil and avanafil work for about the same amount of time — and slightly longer than sildenafil. But tadalafil is by far the longest-lasting of the four ED medications currently on the market. Of course, it’s important to keep in mind that men can react differently to each medication.

The information packets and FDA guidelines for these medications recommend seeking medical advice from a healthcare provider if your erection lasts longer than four hours or if your erection doesn’t go away on its own (a condition called priapism).

Ask your healthcare provider for more information about the half-lives and longevity of these pills. We compared Cialis versus Viagra and Stendra versus Viagra for a more detailed look at some of the more popular ED meds.

Related Articles

Now that you know the answer to “How does ED medication work?” it’s crucial to learn about the possible risks and side effects of ED meds.

Side effects may vary slightly among these medications. But since they work similarly, there are some common side effects, including:

  • Mild headaches

  • Dizziness

  • Muscle aches or back pain 

  • Facial flush

  • Vision issues, including temporary blurry vision 

  • Digestive issues or upset stomach

  • Rhinitis (hint: nasal congestion and a stuffy or drippy nose)

As a newer, second-generation ED med, Stendra (avanafil) may be less likely to cause side effects or other serious issues compared to older medications like Levitra.

However, just as every guy can experience different effectiveness with different medications, some may experience more or fewer side effects than others. We covered all side effects of Viagra and common side effects of tadalafil in our guides.

Drug Interactions

There are also some potentially serious side effects of ED meds, including drug interactions.

All currently available ED medications can temporarily cause slightly lower blood pressure levels, thanks to their effects on smooth muscle tissue and blood flow. This low blood pressure is most often mild and doesn’t usually cause dangerous side effects on men’s health.

That said, if you use nitrates for angina (chest pain) or alpha-blockers and certain other medications to treat hypertension (high blood pressure), the reduction in blood pressure caused by ED medications can be dangerous. 

If you use any nitrates, it’s highly recommended that you don’t use sildenafil, tadalafil, vardenafil, avanafil or other similar medications.

And anyone currently being treated for or with a history of kidney disease, heart disease, heart attack or other cardiovascular condition should discuss treatment options with a healthcare professional.

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While erectile dysfunction is a common health condition, there are several erectile dysfunction treatments out there. So, how do ED pills work?

  • The most common erectile dysfunction medications are PDE-5 inhibitors. They work to help widen the blood vessels in your penis, allowing more blood flow for stronger and longer-lasting erections. Research shows that, when used properly, these ED pills can help improve erectile function.

  • Many of these pills work fairly quickly. Sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) typically start working within 30 to 60 minutes, while avanafil (Stendra) works within 15 to 30 minutes.

  • As with most prescription drugs, ED medications can cause side effects. Some of the most common side effects of ED meds include headaches, dizziness, upset stomach, back pain and nasal congestion.

A healthcare provider can help you determine which ED medication and dose is right for you. You can also learn about more erectile dysfunction treatments that can get your sex life back on track in our guide.

12 Sources

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  2. Sooriyamoorthy, T., Leslie, S.W. Erectile Dysfunction. [Updated 2023 May 30]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Retrieved from
  3. Panchatsharam, P.K., Durland, J., Zito, P.M. Physiology, Erection. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Retrieved from
  4. Dhaliwal, A., Gupta, M. PDE5 Inhibitors. [Updated 2023 Apr 10]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Retrieved from
  5. Frajese, G. V., Pozzi, F., & Frajese, G. (2006). Tadalafil in the treatment of erectile dysfunction; an overview of the clinical evidence. Clinical interventions in aging, 1(4), 439–449. Retrieved from
  6. Katz, E. G., Tan, R. B., Rittenberg, D., & Hellstrom, W. J. (2014). Avanafil for erectile dysfunction in elderly and younger adults: differential pharmacology and clinical utility. Therapeutics and clinical risk management, 10, 701–711. Retrieved from
  7. Label: VIAGRA (sildenafil citrate) tablets. (n.d.). Retrieved from
  8. CIALIS (tadalafil) tablets Label. (n.d.). Retrieved from
  9. STENDRA® (avanafil) tablets, for oral use. (n.d.). Retrieved from
  10. Jackson, G., Arver, S., Banks, I., & Stecher, V. J. (2010). Counterfeit phosphodiesterase type 5 inhibitors pose significant safety risks. International journal of clinical practice, 64(4), 497–504. Retrieved from
  11. Tainted Sexual Enhancement Products. (2023, August 22). FDA. Retrieved from
  12. LEVITRA (vardenafil hydrochloride) tablets, for oral use. (n.d.). Retrieved 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.

Kelly Brown MD, MBA
Kelly Brown MD, MBA

Dr. Kelly Brown is a board certified Urologist and fellowship trained in Andrology. She is an accomplished men’s health expert with a robust background in healthcare innovation, clinical medicine, and academic research. Dr. Brown is a founding member of Posterity Health where she is Medical Director and leads strategy and design of their Digital Health Platform, an innovative education and telehealth model for delivering expert male fertility care.

She completed her undergraduate studies at University of North Carolina at Chapel Hill (go Heels!) with a Bachelor of Science in Radiologic Science and a Minor in Chemistry. She took a position at University of California Los Angeles as a radiologic technologist in the department of Interventional Cardiology, further solidifying her passion for medicine. She also pursued the unique opportunity to lead departmental design and operational development at the Ronald Reagan UCLA Medical Center, sparking her passion for the business of healthcare.

Dr. Brown then went on to obtain her doctorate in medicine from the prestigious Northwestern University - Feinberg School of Medicine and Masters in Business Administration from Northwestern University - Kellogg School of Management, with a concentration in Healthcare Management. During her surgical residency in Urology at University of California San Francisco, she utilized her research year to focus on innovations in telemedicine and then served as chief resident with significant contributions to clinical quality improvement. Dr. Brown then completed her Andrology Fellowship at Medical College of Wisconsin, furthering her expertise in male fertility, microsurgery, and sexual function.

Her dedication to caring for patients with compassion, understanding, as well as a unique ability to make guys instantly comfortable discussing anything from sex to sperm makes her a renowned clinician. In addition, her passion for innovation in healthcare combined with her business acumen makes her a formidable leader in the field of men’s health.

Dr. Brown is an avid adventurer; summiting Mount Kilimanjaro in Tanzania (twice!) and hiking the incredible Torres del Paine Trek in Patagonia, Chile. She deeply appreciates new challenges and diverse cultures on her travels. She lives in Denver with her husband, two children, and beloved Bernese Mountain Dog. You can find Dr. Brown on LinkedIn for more information.

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