Tadalafil

Generic Name: Tadalafil

Brand Names: Cialis (ED), Adcirca (PAH)

Tadalafil is a long-acting PDE5 inhibitor for erectile dysfunction and BPH. Can also be taken daily at low dose.

UrologyMen's Health

Drug Class

Phosphodiesterase Type 5 (PDE5) Inhibitor

Pregnancy

Category B — Animal reproduction studies have not shown fetal harm. Tadalafil is not indicated in women for sexual dysfunction; the pulmonary arterial hypertension indication occasionally arises in pregnancy, where it is used cautiously when alternative therapies are insufficient. Human pregnancy data remain limited.

Available Forms

Oral tablet (2.5 mg, 5 mg, 10 mg, 20 mg — Cialis), Oral tablet (20 mg — Adcirca for pulmonary arterial hypertension), Oral tablet (5 mg generic for daily ED/BPH), Oral suspension (compounded, not commercially available)

What It's Used For

Dosage Quick Reference

These are general dosage guidelines. Your doctor will determine the appropriate dose for your specific situation.

Condition	Starting Dose	Maintenance Dose
Erectile dysfunction (as needed)	10 mg orally at least 30 minutes before sexual activity	5–20 mg as needed; max once daily
Erectile dysfunction (daily dosing)	2.5 mg once daily at the same time each day	5 mg once daily
Benign prostatic hyperplasia (with or without ED)	5 mg once daily	5 mg once daily
Pulmonary arterial hypertension (Adcirca)	40 mg once daily (two 20 mg tablets together)	40 mg once daily
Renal impairment (CrCl 30–50 mL/min, as-needed dosing)	5 mg, no more than once daily	Max 10 mg, no more than every 48 hours
Hepatic impairment (Child-Pugh A or B, as-needed dosing)	10 mg, do not exceed	10 mg, no more than once daily

Side Effects

Common Side Effects:

Headache
Indigestion (dyspepsia)
Back pain
Muscle aches
Flushing
Nasal congestion
Upper respiratory infection

Serious Side Effects (seek immediate medical attention):

Severe hypotension (especially with nitrates)
Priapism (painful erection lasting more than 4 hours)
Sudden vision loss in one or both eyes
Sudden hearing decrease or loss
Chest pain during or after sexual activity
Irregular heartbeat

Drug Interactions

Tadalafil is metabolized primarily by CYP3A4 and exerts vasodilatory effects through cGMP, producing several clinically important interactions.

Nitrates (nitroglycerin, isosorbide mononitrate or dinitrate, amyl nitrite "poppers"): Coadministration causes severe, potentially fatal hypotension. Absolute contraindication. Allow at least 48 hours between the last tadalafil dose and any nitrate administration in an emergency.
Alpha blockers (e.g., tamsulosin, doxazosin, silodosin): Additive blood pressure lowering and risk of symptomatic orthostasis. Patients should be on a stable alpha blocker dose before adding tadalafil; start tadalafil at the lowest dose (2.5 or 5 mg) and titrate cautiously.
Strong CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, itraconazole, clarithromycin): Significantly increase tadalafil exposure. Limit as-needed dose to 10 mg every 72 hours; daily dosing is generally not recommended.
CYP3A4 inducers (e.g., rifampin, carbamazepine, phenytoin, St. John wort): Reduce tadalafil efficacy. Higher doses may be needed, but specific dose recommendations are not established.
Riociguat and other guanylate cyclase stimulators: Combination produces severe hypotension and is contraindicated.
Other antihypertensives (ACE inhibitors, ARBs, calcium channel blockers, beta blockers): Modest additive blood pressure reduction is usually well-tolerated; counsel about possible dizziness on standing.
Alcohol (large amounts): Additive vasodilation and orthostasis. Limit alcohol while taking tadalafil.

Additional Information

Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor used for the treatment of erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension. Distinguished by its prolonged duration of action (up to 36 hours), it offers unique dosing flexibility including daily dosing options that allow for spontaneity in intimate relationships.

Mechanism of Action

Tadalafil selectively inhibits phosphodiesterase type 5 (PDE5), the enzyme responsible for degrading cyclic guanosine monophosphate (cGMP) in the corpus cavernosum, prostatic smooth muscle, and pulmonary vasculature. Sexual stimulation causes local release of nitric oxide, which activates guanylate cyclase to produce cGMP. By inhibiting PDE5, tadalafil allows cGMP to accumulate, enhancing smooth muscle relaxation and blood flow.

In erectile dysfunction, this mechanism promotes penile erection in response to sexual stimulation. In benign prostatic hyperplasia, smooth muscle relaxation in the prostate and bladder improves urinary symptoms. In pulmonary arterial hypertension, pulmonary vasodilation reduces pulmonary vascular resistance and improves exercise capacity.

Available Formulations

Tadalafil is available under different brand names for different indications. Cialis is available as tablets in 2.5 mg, 5 mg, 10 mg, and 20 mg strengths for erectile dysfunction and BPH. Adcirca is available as 20 mg tablets specifically for pulmonary arterial hypertension. Generic tadalafil is now available for all indications. The same molecule is used across all products, but FDA-approved labeling and dosing differ by indication.

FDA-Approved Indications

Tadalafil is FDA-approved for erectile dysfunction in adult males, signs and symptoms of benign prostatic hyperplasia, the combination of erectile dysfunction and BPH, and pulmonary arterial hypertension (WHO Group 1) to improve exercise ability in adults. The ability to treat both ED and BPH with a single medication is particularly valuable for patients with both conditions.

Dosing Guidelines

For erectile dysfunction (as needed): Start at 10 mg prior to anticipated sexual activity; may adjust to 20 mg or decrease to 5 mg based on efficacy and tolerability. For erectile dysfunction (daily): 2.5 mg once daily at approximately the same time, may increase to 5 mg daily. For BPH: 5 mg once daily at approximately the same time. For ED and BPH combined: 5 mg once daily. For pulmonary arterial hypertension: 40 mg (two 20 mg tablets) once daily.

Duration of Action

Tadalafil's extended duration of action (up to 36 hours) distinguishes it from other PDE5 inhibitors. This prolonged effect allows for greater spontaneity and has led to its nickname "the weekend pill." The daily dosing option maintains steady plasma levels, eliminating the need to time medication with anticipated sexual activity.

Important Safety Considerations

All PDE5 inhibitors are contraindicated with nitrates due to severe hypotensive effects that can be life-threatening. The interaction can occur for up to 48 hours after tadalafil use due to its long half-life. Caution is advised with alpha-blockers due to additive hypotension. Tadalafil is contraindicated in patients with severe hepatic impairment and is not recommended with CrCl less than 30 mL/min for daily dosing. Vision loss (NAION) and hearing loss have been reported rarely.

Drug Interactions

Nitrates and nitric oxide donors are absolutely contraindicated. Alpha-blockers may cause additive hypotension; patients should be stable on alpha-blocker therapy before adding tadalafil. Strong CYP3A4 inhibitors (ketoconazole, ritonavir) significantly increase tadalafil levels; dose adjustment may be needed. CYP3A4 inducers (rifampin) may decrease tadalafil efficacy. Alcohol can increase the risk of orthostatic hypotension.

Special Populations

Dose adjustment is required in renal and hepatic impairment depending on severity and indication. For mild to moderate hepatic impairment, doses should not exceed 10 mg for as-needed use. Tadalafil is not indicated for use in women. In patients over 65 years, no dose adjustment is needed based on age alone, but they may be more sensitive to hypotensive effects. Patients with cardiovascular disease should discuss with their physician whether sexual activity is appropriate.

Learn more at MedlinePlus

Frequently Asked Questions

Tadalafil has a half-life of about 17.5 hours — much longer than sildenafil or vardenafil — and remains effective for up to 36 hours after a single dose. This allows for spontaneity rather than precise timing before activity. The longer duration is also why it is useful as a once-daily medication for both ED and benign prostatic hyperplasia.

Tadalafil absorption is unaffected by food, including high-fat meals — another distinction from sildenafil. You can take it before or after eating with similar onset and effect. Grapefruit and grapefruit juice can modestly raise tadalafil levels and are best limited.

Do not take tadalafil if you use any nitrate medication (nitroglycerin, isosorbide), the pulmonary hypertension drug riociguat, or recreational "poppers." It is also generally avoided in unstable cardiovascular disease, recent stroke or heart attack within 90 days, severe hepatic impairment, and severe hypotension. Discuss your full medical history with your prescriber before starting.

Seek emergency care immediately. Priapism — a sustained painful erection — can permanently damage erectile tissue if untreated. While rare with tadalafil, it requires urgent evaluation, often by urology. Do not wait it out, and avoid additional doses of any PDE5 inhibitor until you are evaluated.

Tadalafil improves the physical erectile response by enhancing blood flow when sexual stimulation occurs. It does not increase libido or cause spontaneous erections without arousal. If lack of desire is the main issue, addressing relationship factors, depression, low testosterone, sleep, and medication side effects with your physician is more likely to help.

Mild bluish color tinting and altered light perception have been reported but are uncommon. Sudden vision loss (NAION) or sudden hearing loss are rare but serious. Stop tadalafil and seek prompt evaluation if either occurs. Patients with a prior history of NAION or "small optic disc" anatomy should discuss their risk before starting therapy.

Questions to Ask Your Doctor

Consider discussing these topics at your next appointment:

✓Is tadalafil safe for my heart, considering my current cardiovascular history?
✓Do any of my current medications — especially nitrates or alpha blockers — interact with tadalafil?
✓Should I try as-needed dosing or daily low-dose tadalafil based on my goals?
✓Could my symptoms be related to low testosterone, depression, or another underlying condition we should evaluate?
✓What red-flag symptoms (chest pain, vision change, prolonged erection) should make me seek urgent care?

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Related Health Conditions

This medication is commonly used to treat or manage the following conditions:

Attention Deficit Hyperactivity Disorder (ADHD)

ADHD is a neurodevelopmental disorder marked by inattention, hyperactivity, and/or impulsivity, stemming from complex interactions between genetics, brain differences, and environmental factors, not poor parenting.

Learn More

Benign Prostatic Hyperplasia (BPH)

Benign Prostatic Hyperplasia (BPH), or enlarged prostate, is a common, non-cancerous condition in aging men causing urinary symptoms due to prostate growth pressing on the urethra.

Learn More

Medical Disclaimer: This information is for educational purposes only and should not be considered medical advice. Always consult with your healthcare provider before starting, stopping, or changing any medication. Your doctor can provide personalized recommendations based on your specific health condition and medical history.