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Cialis 20mg: How it Compares to Other ED Treatments

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 12/22/2021

Tadalafil, the active ingredient in the medication Cialis®, is one of the most effective and widely used options on the market for treating erectile dysfunction, or ED.

As with other erectile dysfunction medications, Cialis is available in a variety of dosages. One of the most common forms of Cialis is a 20mg tablet, which is designed for use when needed as a treatment for erectile dysfunction.

If you suffer from erectile dysfunction, using Cialis at a 20mg dosage may make it easier for you to get and keep an erection. However, the 20mg dosage of Cialis isn’t the only way that you can use Cialis, nor is it the only option for treating ED.

Below, we’ve explained how Cialis 20mg works, as well as how it compares to other dosages of Cialis and FDA-approved ED treatments such as Viagra® (sildenafil), Levitra® (vardenafil) and Stendra® (avanafil).

How Cialis Works

How does Cialis work? At a simple level, Cialis works by increasing the amount of blood that can flow into your penis when you receive sexual stimulation.

Tadalafil, the active ingredient in Cialis, belongs to a class of medications referred to as PDE5 inhibitors. It works by inhibiting the actions of the enzyme phosphodiesterase type 5, which is responsible for regulating blood flow to the erectile tissue of your penis.

Erections are all about blood flow. When you’re sexually aroused, your nerves signal to tissue inside your penis called the corpora cavernosa, which relaxes and allows blood to flow in and create pressure.

When you take Cialis, it becomes easier for blood to flow into the corpus cavernosa — the soft, spongy tissue of your penis that fills with blood to become erect. This increased blood flow can help you to get and maintain an erection when you feel sexually aroused. 

Cialis differs from other ED medications in several ways, the biggest of which is its long duration of action. 

How long does Cialis last? Compared to other ED medications, such as Viagra® (sildenafil) and Levitra® (vardenafil), both of which last for a few hours each, Cialis offers long-lasting effects, with a single dose generally providing relief from ED symptoms for up to 36 hours.

Thanks to its long-lasting effects, Cialis has earned a reputation as a “weekend pill” for treating erectile dysfunction. 

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Cialis Side Effects

Like other ED medications, Cialis can cause side effects. Most side effects from Cialis are mild, although in rare cases, medications such as Cialis may cause more serious or bothersome side effects. 

Common side effects of Cialis include:

  • Headaches. Headaches can occur with all ED medications, including Cialis. According to a 2008 review, headaches were reported by 15 percent of men who used Cialis at a dosage of 20mg, making them the most commonly reported adverse effect.

  • Indigestion and heartburn. Cialis and other medications for ED can cause indigestion, or heartburn. This side effect occurs in eight percent of men who use Cialis at a 20mg dosage.

  • Back and/or muscle pain. Cialis can cause back pain and/or myalgia, a form of muscle aches and muscle pain. Three to five percent of men who use Cialis at a dosage of 10 to 20mg report experiencing this side effect.

  • Flushing. Because of its effects on your blood vessels, Cialis may cause you to develop facial flushing. This side effect occurs in around three percent of men who use Cialis. It can also occur with other medications for ED.

  • Nasopharyngitis (cold symptoms). A small percentage of men who use Cialis for ED experience cold-like symptoms, such as nasal congestion (or “stuffy nose”).

In rare cases, Cialis and other medications for ED may cause more serious side effects, such as dizziness, reduced blood pressure, hearing problems, loss of vision or chest pain. It’s important to inform your healthcare provider immediately if you experience any concerning symptoms. 

Cialis and other ED medications may also cause priapism, a form of painful, prolonged erection that can damage the tissue of your penis. This is a highly uncommon side effect with few case reports in medical literature.

Our guide to priapism provides more information about this side effect. If you start to develop a long-lasting, uncomfortable or painful erection after taking Cialis, make sure to seek immediate medical help. 

Cialis Drug Interactions

Cialis can interact with other medications. Some medications, including those prescribed to treat heart disease or hypertension, can cause dangerous and potentially life threatening side effects when used with Cialis or generic tadalafil.

If you’re prescribed Cialis, it’s important not to take it with nitrates or other heart medications. If used together, these medications can cause a sudden, significant drop in blood pressure. These effects may also occur with street drugs that contain nitrates, such as “poppers.”

To avoid interactions, make sure to inform your healthcare provider about all of the medications you currently use or have recently used before taking Cialis. 

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Cialis 20mg vs. Other Cialis Dosages

Cialis comes in oral tablet form and is available in several dosages, ranging from just 2.5mg per tablet to 5mg, 10mg and 20mg. The 20mg version of Cialis is currently the maximum dose that’s available. 

Some of these Cialis dosages are designed for use as needed (used only before sex), whereas others are designed for use every day. We’ve explained how each cialis dosage differs in more detail below.

Cialis 10mg

The FDA recommends the 10mg version of Cialis as a starting dosage for use as needed as a treatment for erectile dysfunction. If you suffer from ED and want to use Cialis as needed, it’s likely that your healthcare provider will recommend this dosage.

Research shows that the 10mg dosage of Cialis works well for the majority of men affected by erectile dysfunction. 

In clinical trials, 68 percent to 77 percent of men with erectile dysfunction who used Cialis at a 10mg dosage were able to have penetrative sex with their partner, compared to 46 percent to 55 percent of men given a non-therapeutic placebo.

As you may expect, Cialis 10mg has a moderately higher rate of side effects than the 5mg and 2.5mg versions of this medication, and a slightly lower rate of side effects than Cialis 20mg.

Cialis 20mg

Cialis is also available as a 20mg tablet. This version of Cialis is the strongest dosage that has been approved for use by the FDA and, just like the 10mg version of Cialis, is designed for use as needed before you have sex.

Your healthcare provider may prescribe the 20mg version of Cialis if you don’t get satisfactory results from the 10mg dosage.

Studies of Cialis 20mg have found that it’s typically more effective than lower-dose versions of Cialis.

In clinical trials, 76 percent to 85 percent of men given this dosage could successfully have sex with their partner, versus 68 percent to 77 percent of men who used Cialis at a 10mg dosage.

Cialis 20mg is slightly more likely to cause certain side effects, such as headache or dyspepsia (indigestion), than the 10mg dosage of Cialis. However, the increased risk of experiencing side effects is fairly small.

Even at the highest dosage of Cialis, side effects are still uncommon. In clinical trials, the most common side effect of Cialis, headache, was only reported by 15 percent of men who used the 20mg version of the medication.

Cialis 5mg

Cialis is available as a 5mg tablet. This version of Cialis can be taken daily (we’re explained this in more detail below) or as needed to treat erectile dysfunction.

Your healthcare provider may suggest using Cialis 5mg if you experience significant side effects from the 10 or 20mg dosages, or if you think that these dosages are more than needed in order to treat your erectile dysfunction.

Research shows that when used as needed, Cialis 5mg is more effective than a non-therapeutic placebo but less effective at treating ED than Cialis 10mg or 20mg.

It’s also slightly less likely to cause common ED medication side effects, such as headache and dyspepsia (indigestion).

Daily Cialis (Cialis 5mg and 2.5mg)

Cialis is also available as a daily-use medication at dosages of 5mg and 2.5mg. These versions of Cialis are designed to be taken daily at the same time, instead of as needed before you have sex.

Taking Cialis daily rather than as needed has some advantages, such as fewer common side effects and a simple dosage schedule. It also means that you’ll be ready to have sex any time during the day, rather than just after taking your medication.

However, it also has some disadvantages, such as side effects that may be more persistent or bothersome. We’ve discussed these in more detail in our full guide to daily-use Cialis.

Cialis 20mg vs. Viagra (Sildenafil)

Cialis is often compared to other ED medications such as Viagra (sildenafil). As a treatment for erectile dysfunction, the 20mg dosage of Cialis offers several advantages compared to Viagra: 

  • It’s longer lasting. The effects of Cialis 20mg last for approximately 36 hours, making it a very long-lasting treatment for erectile dysfunction. In comparison, the effects of Viagra tend to fade away after three to five hours. Due to its longer duration of action, as-needed Cialis may be a better choice for you if you want to treat erectile dysfunction for the entire day with a single dose of medication.

  • It’s less affected by food. Cialis is not affected by food, meaning you can take it before or after eating. This may be useful if you plan to take Cialis with dinner in order to have sex later in the nighttime. While it’s also okay to take Viagra with food, taking Viagra after a meal that contains lots of fat may affect the drug’s absorption and slow down its effects.

On the other hand, the 20mg dosage of Cialis also has a variety of disadvantages compared to Viagra:

  • In certain circumstances, it might be too long-lasting. Cialis is famous for providing relief from ED for longer than other medications. However, if you only need to treat your ED symptoms for a night, the 36-hour effects of Cialis may be more than needed.

  • It may cause longer-lasting side effects. Because of Cialis’s long half-life and duration of action, it can cause more persistent side effects than other ED medications. This may be an issue if you’re prone to side effects from PDE5 inhibitors.

Ultimately, Cialis and Viagra are different medications that treat the same condition. The biggest advantage of Cialis is its long duration of action, while the main advantage of Viagra is that it’s a great medication for use as-needed for a single night of sex. There are also chewable Cialis and Viagra, which we detail in our blog.

Our Cialis vs. Viagra guide goes into more detail on the main advantages and disadvantages of both medications, from effectiveness to side effects, ease of use, safety and more.

Cialis 20mg vs. Other ED Medications

In addition to Cialis, other medications, such as Levitra (vardenafil) and Stendra (avanafil) can also treat erectile dysfunction. Like Viagra, these medications differ from the 20mg dosage of Cialis in several ways:

  • Levitra. Levitra typically lasts for slightly longer than Viagra, but is much shorter-acting than Cialis. This makes it a good alternative to Cialis if you’d like to use ED medication as needed, rather than once per 36 hours. Our more detailed Levitra vs. Cialis comparison provides more information on how these popular ED medications differ.

  • Stendra. Stendra is a new medication for ED. It starts working in as little as 15 minutes, making it a much faster-acting medication than Cialis. On average, a dose of Stendra provides relief from ED for approximately four to six hours.As a newer ED medication, Stendra has a lower risk of causing certain side effects than Cialis.

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Is Cialis 20mg Right For You?

The 20mg dosage of Cialis is a good option if you want relief from erectile dysfunction that lasts for an entire day or longer, or if you’ve previously used Cialis at a 5mg or 10mg dose and didn’t experience satisfactory effects. 

However, it’s slightly more likely to cause side effects than the 10mg version of Cialis, which is why healthcare professionals typically prescribe Cialis at a lower dosage first.

We offer both brand name Cialis and generic tadalafil online. We also offer a range of other ED medications, including Viagra, generic sildenafil and Stendra (avanafil). 

All of these medications are effective at treating ED, with each offering its own range of unique advantages and disadvantages.

Worried about ED? Our complete guide to erectile dysfunction explains everything you need to know about this common sexual performance issue, from the top causes of ED to your options for treating erectile dysfunction and enjoying a fulfilling, satisfying sex life. 

Related read: Cialis 20mg price

8 Sources

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.

  1. Dhaliwal, A. & Gupta, M. (2021, June 25). PDE5 Inhibitors. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK549843/
  2. Erection Ejaculation: How It Occurs. (2020, November 27). Retrieved from https://my.clevelandclinic.org/health/articles/10036-erection-ejaculation-how-it-occurs
  3. CIALIS (tadalafil) tablets, for oral use. (2011, October). Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2011/021368s20s21lbl.pdf
  4. Coward, R.M. & Carson, C.C. (2008, December). Tadalafil in the treatment of erectile dysfunction. Therapeutics and Clinical Risk Management. ​​4 (6), 1315–1330. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2643112/
  5. Tadalafil. (2016, April 15). Retrieved from https://medlineplus.gov/druginfo/meds/a604008.html
  6. VIAGRA® (sildenafil citrate) tablets, for oral use. (2017, December). Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2017/020895s048lbl.pdf
  7. 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 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4155803/
  8. STENDRA® (avanafil) tablets, for oral use. (2018, August). Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/202276s018lbl.pdf

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.