The Wellness Collective

What to Know About Tadalafil

Mariah Powers
February 5, 2026

Reviewed by Ashley Robinson, PharmD, Pharmacy Manager for TelyRx

Tadalafil, best known by its brand name Cialis, is used to treat erectile dysfunction (ED). It is also FDA-approved to treat the urinary symptoms of an enlarged prostate (Benign Prostatic Hyperplasia, or BPH). Tadalafil belongs to a class of drugs called PDE-5 inhibitors.

Its main feature is a long-lasting effect, with a single “as-needed” dose remaining effective for up to 36 hours, earning it the nickname “the weekend pill.” It is also available in a lower, once-daily dose for those who prefer not to plan for sexual activity.

Common side effects include headache, indigestion, back pain, and muscle aches. A very rare but serious side effect is priapism; an erection lasting over 4 hours.

How does Tadalafil work?

Tadalafil is a PDE-5 inhibitor. It works by blocking an enzyme called PDE-5.

When you are sexually aroused, your body releases nitric oxide, which increases levels of cGMP and relaxes smooth muscle, allowing more blood to flow into the penis. Tadalafil blocks PDE-5, the enzyme that breaks down cGMP, helping this process last longer. It does not cause an erection without sexual stimulation.

Drug facts

Common Brands	Cialis, Adcirca, Alya
Drug Class	Phosphodiesterase-5 (PDE-5) inhibitor
Generic Status	Generic version of Cialis
Availability	Prescription Only

Dosing

Note: Dosing information below is educational only. Your prescribing physician will determine your specific dose based on your individual health needs.

Dosing for tadalafil is flexible and depends on the condition and your preference.

For ED (As-Needed)
- The typical starting dose is 10 mg, taken at least 30 minutes before sexual activity.
- This dose can be increased to 20 mg or decreased to 5 mg based on effectiveness and side effects.
- The effects can last for up to 36 hours. Do not take more than one dose in a 24-hour period.
For ED (Once-Daily)
- The dose is 2.5 mg or 5 mg taken once a day, at the same time every day.
- This allows for spontaneous sexual activity without the need to time a pill.

FDA-approved uses

Erectile Dysfunction (ED) – The most common use.
Benign Prostatic Hyperplasia (BPH) – To treat the urinary signs and symptoms of an enlarged prostate.
ED and BPH Together – For men who have both conditions.
Pulmonary Arterial Hypertension (PAH) – Tadalafil is also sold under the brand name Adcirca to treat high blood pressure in the lungs. You should never take both Cialis and Adcirca.

Common off-label uses

You may see Mounjaro prescribed for uses that are not “FDA-approved.” This is a very common and legal practice called “off-label” prescribing, where a doctor uses their clinical judgment to prescribe a drug for a different (but well-researched) purpose.

Mounjaro is widely prescribed “off-label” for chronic weight management in adults who are overweight or obese. While Mounjaro is not officially FDA-approved for weight loss, its active ingredient, tirzepatide, is approved for this use under the brand name Zepbound.

Side effects

These side effects are often mild and may go away as your body adjusts.

Common Side Effects

Headache
Indigestion or upset stomach
Back pain
Muscle aches
Flushing (facial redness)
Runny or stuffy nose

Serious Side Effects

Serious side effects are rare, but it’s important to know what to look for if they do occur.

Stop taking tadalafil and seek medical help immediately if you experience:

Priapism – An erection that is painful or lasts longer than 4 hours. This is a medical emergency that can cause permanent damage.
Sudden Vision Loss – A sudden decrease or loss of vision in one or both eyes.
Sudden Hearing Loss – A sudden decrease in hearing or ringing in the ears (tinnitus).
Severe Low Blood Pressure – Dizziness, lightheadedness, or fainting.
Signs of Heart Attack/Stroke – Chest pain, sudden numbness or weakness, severe headache, or confusion.
Serious Allergic Reaction – Rash, hives, swelling of the face, lips, or throat, and difficulty breathing.

Call your doctor immediately if you experience any concerning or prolonged symptoms.

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Pharmacist tips

The 36-Hour Window – The biggest advantage of the “as-needed” dose is its long duration. A single pill allows for sexual activity for up to 36 hours.
Nitrates are a “No” – NEVER take tadalafil if you take nitrate medications for chest pain (like nitroglycerin), high blood pressure (like isosorbide mononitrate) or use recreational “poppers” (amyl nitrite). The combination can cause a sudden, life-threatening drop in blood pressure.
Erection Over 4 Hours? Go to the ER – A prolonged erection (priapism) is a serious emergency. If your erection lasts more than 4 hours, go to the nearest emergency room.
With or Without Food – Tadalafil works well either way. Unlike some other ED pills, a meal won’t significantly affect its absorption.
Watch the Alcohol – Limit your alcohol intake. Drinking alcohol can increase the side effects of dizziness and headache and can make it harder to get an erection.
No “Double Dosing” – Never take tadalafil with other PDE-5 inhibitors like sildenafil (Viagra) or vardenafil (Levitra).
Daily Dose vs. As-Needed – The daily dose (2.5mg or 5mg) is great for men who prefer spontaneity. The as-needed dose (10mg or 20mg) is better for men who have sex less frequently and prefer a stronger, single dose.

Drug interactions

Tadalafil can interact with many medications. The most critical interaction is with nitrates.

DO NOT TAKE TADALAFIL if you take:

Nitrates (nitroglycerin, isosorbide mononitrate, amyl nitrite “poppers”).
Guanylate Cyclase (GC) Stimulators (Riociguat).

Use caution and talk to your doctor if you take:

Alpha-blockers – (tamsulosin for BPH) as this combination can cause low blood pressure.
Blood Pressure Medications – Tadalafil can have an additive effect.
CYP3A4 Inhibitors – (ketoconazole, clarithromycin, grapefruit juice), which can increase the level of tadalafil in your blood.
Other PDE-5 Inhibitors – sildenafil, vardenafil.

Always give your doctor and pharmacist a complete list of all your medications, vitamins, and supplements to check for potential interactions.

FAQs

How long does Tadalafil (Cialis) last?

The “as-needed” dose (10 mg or 20 mg) is effective for up to 36 hours. This doesn’t mean you’ll have an erection for 36 hours, but that the medication will be in your system to help you achieve an erection with stimulation during that time.

What’s the difference between Cialis and Viagra?

The main difference is duration. Viagra (sildenafil) works for about 4 to 6 hours. Cialis (tadalafil) works for up to 36 hours. Cialis also has a daily-dose option, while Viagra is only taken as needed.

Can I take Tadalafil every day?

Yes. The 2.5 mg and 5 mg doses are designed to be taken once daily. This allows for spontaneous sexual activity anytime, rather than having to time a pill before sex.

Can I cut a 20mg Tadalafil tablet in half?

No. Tadalafil tablets are not scored and are designed to be swallowed whole. Cutting them can lead to an uneven or incorrect dose.

Does Tadalafil make you last longer during sex?

Tadalafil treats erectile dysfunction (the ability to get/keep an erection). It does not treat premature ejaculation (how long it takes to climax).

Why does Tadalafil cause back pain?

Back pain and muscle aches are unique common side effects of tadalafil. This is thought to be related to its effect on the PDE-11 enzyme, which is found in muscle tissue. The pain is temporary and usually goes away within 1-2 days.

Can I drink grapefruit juice with Tadalafil?

It’s best to avoid it. Grapefruit juice can inhibit an enzyme in your liver that breaks down tadalafil, leading to higher levels of the medication in your blood and an increased risk of side effects.

Compare medications

Compared: Tadalafil, Sildenafil, Vardenafil, or Avanafil?

Tadalafil is in the same class as several other well-known ED medications. The main differences are in their duration, onset of action, and how they are affected by food.

Tadalafil (Cialis) – The “weekend pill,” notable for its extremely long 36-hour duration and the option for a low, once-daily dose.
Sildenafil (Viagra) – The original “little blue pill,” works for 4-6 hours and is most effective when taken on an empty stomach.
Vardenafil – Has a similar profile to sildenafil, with a 4-6 hour duration, and is known for being a potent option.
Avanafil (Stendra) – The newest option, known for its very fast onset of action (as quickly as 15 minutes for some men).

Disclaimer

Important: Information on this page is for educational purposes only. Prescribing decisions are made by independent, licensed providers. TelyRx operates technology-enabled pharmacies and a telehealth platform that connects patients with board-certified licensed providers. Prescriptions, when provider-approved and issued, are filled and shipped by TelyRx-affiliated pharmacies. We do not employ physicians or make prescribing decisions. Learn more about our editorial standards here.

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