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What Is Tadalafil? Side Effects, Usage, Dosage & More

By Sarah Malka, MD
Medically reviewed
April 5, 2021

Tadalafil (Cialis) is a prescription medication approved by the Food and Drug Administration (FDA) to treat symptoms of erectile dysfunction (ED), benign prostatic hyperplasia (BPH) and pulmonary arterial hypertension (PAH). 

For most men affected by ED and BPH, and for anyone with PAH, tadalafil is a safe and effective treatment option. It’s only available via prescription, so it’s important to talk to your doctor to determine if tadalafil is right for you. 

To help you prepare for that conversation, this article describes who can take tadalafil, how to take it, how long it lasts, and its side effects, drug interactions, alternatives, and cost.

Skip Ahead: What Is Tadalafil? | Uses | Side Effects | How to Take | Precautions | Drug Interactions | Cost | Tadalafil vs. Sildenafil vs. Vardenafil | Can You Buy Tadalafil Online? | When to See a Doctor

What Is Tadalafil?

Tadalafil is a prescription drug that comes as an oral tablet. It’s also sold under the brand names Cialis and Adcirca.

What Is Tadalafil Used For?

Tadalafil is a popular medication for the treatment of erectile dysfunction (ED). It can also be used to treat benign prostatic hyperplasia (BPH, or an enlarged prostate) and pulmonary arterial hypertension (PAH, or high blood pressure in the arteries of the lungs and heart). 

Tadalafil is a phosphodiesterase-5 enzyme (PDE5) inhibitor. In the treatment of ED, it works by relaxing the penile muscles, expanding blood vessels that go into the penis, and improving penile blood flow during sexual stimulation. This ultimately helps men get and maintain better erections. 

In the treatment of BPH, tadalafil helps relax the bladder and prostate muscles to improve symptoms such as painful or frequent urination.

In the treatment of PAH, tadalafil can help relax blood vessels in the lungs to allow blood to flow more easily and improve the ability to exercise.

Side Effects

Like all medications, some side effects can occur when taking tadalafil. The most common side effects include:

Additional side effects can be more serious:

  • Dizziness
  • Erections that last longer than four hours
  • Hearing loss
  • Vision problems

If you experience dizziness, an erection that lasts longer than four hours, hearing loss, vision problems, or any other unusual side effects, contact your healthcare provider immediately.

How to Take Tadalafil

Take tadalafil with a glass of water with or without food either once daily or as needed for ED. If you’re taking it as a daily medication, remember to take it at the same time every day. 

The most common recommended dosage of tadalafil for ED is 10 mg (milligrams) as needed.

When prescribed for the treatment of BPH, most doctors recommend 5 mg, and for PAH, the recommended dose is 40 mg (taken as two 20-mg pills). 

However, when it comes to dosing and instructions, follow your doctor’s recommendation. They will take into account not only your condition but also your age, symptoms, other existing medical conditions, and how you react to the first dose to help prescribe the right dosage for you.

How long it lasts

Tadalafil takes about 30 minutes to take effect (but may take up to two hours) and can last in your system for up to 36 hours.

Regardless of the condition you’re treating, do not take more than one dose every 24 hours.

Can women take tadalafil?

Women with PAH can take tadalafil, but it is not recommended for women who are pregnant or breastfeeding.

If you are pregnant, plan to become pregnant, or breastfeed, talk to your doctor about the right PAH treatment options for you.

Precautions 

Whenever you start a new medication, it’s important to talk to your doctor about any known allergies or conditions that may affect the medication. Specifically, tadalafil may not be suitable for people with the following conditions: 

  • Heart disease: People with ED may be at a greater risk for having heart failure, heart attack or stroke. Therefore, tadalafil or other ED medication may have heart health benefits. However, talk to your doctor.
  • High or low blood pressure: If you have low blood pressure, high blood pressure, coronary artery disease, arrhythmias, or have had heart attacks or strokes in the past, tadalafil medication may not be safe for you. 
  • Liver or kidney disease: Tadalafil is not recommended for people with liver or kidney problems.
  • Sickle cell anemia: Tadalafil may cause adverse effects in people with sickle cell anemia.
  • Peyronie’s disease: Speak with your doctor if you have a curved or deformed penis.
  • Retinitis pigmentosa: Speak with your doctor if you have this rare genetic eye disease or any other chronic eye condition.
  • Bleeding disorders or peptic ulcers: Your doctor may want to monitor you closely if you have either of these conditions.
  • Leukemia, multiple myeloma and other cancers: Tadalafil may cause serious side effects in people with certain cancers.

Drug Interactions

Tadalafil can interact with medications. Talk with your healthcare provider if you’re on any of the following: 

  • Alpha blockers: Medications like doxazosin and tamsulosin used to treat hypertension can interact with tadalafil, producing dangerous side effects.
  • Nitrates: Nitrates, nitroglycerin-based medication, and other medications prescribed to treat chest pain and angina (including amyl nitrite) can cause a negative reaction when combined with tadalafil or other PDE5 inhibitors. 
  • Riociguat (Adempas): If you take riociguat for PAH, check with your healthcare provider before taking tadalafil.
  • St. John’s wort: Some herbal and over-the-counter remedies can interact negatively with tadalafil. If you’re taking any herbal products, including St. John’s wort, be sure to tell your healthcare provider.
  • Antibiotics: Some antibiotics, including clarithromycin, erythromycin, and telithromycin, can increase blood levels of tadalafil, causing unwanted side effects. This can include priapism, or prolonged erections. Additionally, rifampin and other types of antibiotics may lower the level of tadalafil in your blood, reducing its efficacy.
  • HIV medication: Certain HIV medications and protease inhibitors can also raise levels of tadalafil in your blood, causing unwanted side effects and in some cases leading to priapism. Consult with your doctor if you’re currently taking ritonavir or lopinavir.
  • Oral antifungals: Some antifungals like ketoconazole and itraconazole may raise tadalafil levels in your blood.
  • Other ED medications: Sildenafil (Viagra) and vardenafil (Levitra) should not be combined with tadalafil, as this may increase the risk of side effects.

It should also be noted that tadalafil is not a replacement for safe sex practices, nor can it prevent sexually transmitted diseases.

Alcohol and food interactions

Here are some other considerations to make before taking tadalafil:

  • Alcohol: Consuming large quantities of alcohol while taking tadalafil can cause unwanted side effects such as dilated blood vessels, dizziness, headache, fast heartbeat, and low blood pressure. Talk with your doctor about your regular alcohol consumption before starting tadalafil.
  • Grapefruit: Eating grapefruit or drinking grapefruit juice can increase the levels of tadalafil in your blood, raising your risk of side effects like headache, nausea, and dizziness.

Cost of Tadalafil

The cost of tadalafil varies depending on the recommended dosage and your insurance. 

With K Health, tadalafil costs $1.80 per 10-mg dose, while other providers may charge up to $44 for the same dose. 

Alternatives to Tadalafil: Tadalafil vs. Sildenafil vs. Vardenafil

For the treatment of ED, two popular alternatives to tadalafil exist: sildenafil (Viagra) and vardenafil (Levitra). Here are how the two compare to tadalafil.

Sildenafil vs. tadalafil

Sildenafil is often the first-line medication offered by doctors to treat ED because it’s been on the market longest and its side effects and drug interactions are well known. It can be prescribed as an oral tablet, oral liquid, or subcutaneous injection. 

Unlike tadalafil, sildenafil is designed specifically for use as needed, meaning you’ll need to take it shortly before sexual activity. It can take anywhere from 30 minutes to an hour to go into effect and stays in your system for just 4-5 hours, whereas tadalafil can stay in your system for up to 36 hours and can help men become erect anytime during that window.

Sildenafil also requires a higher dosage than tadalafil, with a recommended dose of 50 mg. Unlike tadalafil, you cannot take sildenafil with food, as it’s most effective when taken on an empty stomach.

Sildenafil can also be used to treat PAH, but it cannot be not used to treat BPH.

Vardenafil vs. tadalafil

Vardenafil is an oral medication to treat ED. It works similarly to sildenafil but requires a lower dosage. Like sildenafil, it lasts for just 4-5 hours in your system, unlike tadalafil which can stay in your system for up to 36 hours.

Like tadalafil, the recommended initial dose of vardenafil is 10 mg, though some doctors prescribe anywhere from 5-20 mg. It takes 30 minutes to two hours to take effect and can be taken with or without food, one hour before sexual activity. 

Can You Buy Tadalafil Online?

Tadalafil is only available with a prescription, but you can buy it from some providers and pharmacies online. With K Health, you’ll find the lowest possible cost for tadalafil—and shipping and doctors consultations are always free.

When to See a Doctor

If you’re struggling with symptoms of ED, BPH, or PAH, talk with your doctor to see if tadalafil is right for you. It’s also important to discuss any existing conditions, medications, supplements, and alcohol consumption to determine whether or not tadalafil may cause any negative interactions.

If you’ve already started tadalafil but experience unwanted side effects, talk to your doctor. They may recommend a change in dosage or medication.

How K Health Can Help 

K Health provides a simple, accessible option for ED treatment. Chat with a doctor on your phone to determine whether you are experiencing ED. Your doctor will then prescribe you medication, which can be picked up at a local pharmacy or shipped discreetly directly to you. They will also provide a longer-term care plan to help you manage your ED.

Frequently Asked Questions

What is tadalafil?
Tadalafil is a prescription drug that comes as an oral tablet. It’s also sold under the brand names Cialis and Adcirca.
What is tadalafil used for?
Tadalafil is used to treat erectile dysfunction (ED), benign prostatic hyperplasia (BPH), and pulmonary arterial hypertension (PAH).
How long does tadalafil last?
Tadalafil can last in your system for up to 36 hours. In the treatment of erectile dysfunction (ED), it can help men get erect at any time during that window.
How does tadalafil work?
Tadalafil is a phosphodiesterase-5 (PDE5) inhibitor. In the treatment of ED, tadalafil works by relaxing the penile muscles, expanding blood vessels that go into the penis, and improving penile blood flow during sexual stimulation. This helps get and maintain better erections. In the treatment of BPH, tadalafil helps to relax the bladder and prostate muscles to improve symptoms like painful or frequent urination. And in the treatment of pulmonary arterial hypertension (PAH), tadalafil can help to relax blood vessels in the lungs to allow blood to flow more easily and improve the ability to exercise.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Sarah Malka, MD

Dr. Sarah Malka is a board certified emergency medicine physician with K Health. She completed her residency at Harvard Medical School.