Tadalafil
Brand names: Cialis (ED & BPH) · Adcirca · Alyq (pulmonary arterial hypertension) · Generic available
What Is Tadalafil?
Tadalafil is a prescription medication belonging to the phosphodiesterase type 5 (PDE5) inhibitor drug class. It was first approved by the FDA in 2003 under the brand name Cialis for the treatment of erectile dysfunction in men. It was later approved for benign prostatic hyperplasia and, under the brand names Adcirca and Alyq, for pulmonary arterial hypertension — a serious condition involving high blood pressure in the arteries of the lungs.
What distinguishes tadalafil from other PDE5 inhibitors such as sildenafil (Viagra) is its exceptionally long duration of action — up to 36 hours — which earned it the popular nickname "the weekend pill." This extended window of effectiveness gives patients greater spontaneity compared to shorter-acting alternatives. It is available in both as-needed formulations and as a lower-strength daily tablet for continuous management of ED or BPH.
What Is Tadalafil Used For?
Tadalafil is approved by the FDA for several distinct indications. A healthcare provider will determine which use is appropriate based on a patient's individual health profile and needs.
- Erectile dysfunction (ED): Helps men achieve and maintain an erection sufficient for sexual activity when taken as needed or as a daily tablet
- Benign prostatic hyperplasia (BPH): Relaxes smooth muscle in the prostate and bladder neck, improving urinary flow and reducing symptoms such as urgency, frequency, and incomplete emptying
- Pulmonary arterial hypertension (PAH): Under the brand names Adcirca and Alyq, tadalafil dilates pulmonary arteries to reduce blood pressure in the lungs and improve exercise capacity
- Combined ED and BPH: A single daily tablet can address both conditions simultaneously in men who have both diagnoses
How Does Tadalafil Work?
Tadalafil works by selectively inhibiting an enzyme called phosphodiesterase type 5 (PDE5). Under normal circumstances, PDE5 breaks down a signaling molecule called cyclic guanosine monophosphate (cGMP). When PDE5 is blocked, cGMP levels rise — and elevated cGMP causes smooth muscle cells in blood vessel walls to relax. This relaxation widens the blood vessels (vasodilation), allowing more blood to flow through them.
In erectile dysfunction, this vasodilation increases blood flow into the corpora cavernosa of the penis, facilitating erection in response to sexual stimulation. In BPH, it relaxes smooth muscle in the prostate gland and bladder neck, reducing urinary obstruction. In pulmonary arterial hypertension, it dilates the pulmonary arteries, reducing the workload on the right side of the heart. Tadalafil also weakly inhibits PDE11, an enzyme found in skeletal muscle — this is thought to be responsible for the back pain and muscle aches that are uniquely associated with tadalafil among PDE5 inhibitors.
Side Effects
Common Side Effects
- Headache
- Flushing (warmth or redness of the face, neck, or chest)
- Nasal congestion or runny nose
- Dyspepsia (indigestion, upset stomach, heartburn)
- Back pain and muscle aches — more common with tadalafil than other PDE5 inhibitors due to PDE11 inhibition
- Limb pain
- Dizziness, particularly when standing up quickly
Serious Side Effects
- Sudden vision loss in one or both eyes — a rare condition called non-arteritic anterior ischemic optic neuropathy (NAION). Stop tadalafil immediately and contact a doctor or emergency services.
- Sudden hearing loss, with or without ringing in the ears or dizziness
- Priapism — a painful erection lasting more than 4 hours, which can cause permanent erectile damage if not treated promptly
- Severe hypotension — dangerously low blood pressure, especially if tadalafil is taken with nitrates or alcohol
- Cardiovascular events — chest pain or irregular heartbeat during sexual activity; stop and seek emergency care
Drug Interactions
Tadalafil has several clinically important drug interactions. Always inform your healthcare provider and pharmacist of all medications, supplements, and recreational drugs you use before starting tadalafil.
| Drug / Drug Class | Interaction | Clinical Significance |
|---|---|---|
| Nitrates (nitroglycerin, isosorbide mononitrate, amyl nitrite "poppers") | Both drugs lower blood pressure; combined effect can cause severe, life-threatening hypotension | ABSOLUTE CONTRAINDICATION — never combine |
| Alpha-blockers (doxazosin, tamsulosin, alfuzosin) | Additive blood pressure lowering; risk of symptomatic hypotension, dizziness, and fainting | High — requires careful management and timing; often used together for BPH under medical supervision |
| CYP3A4 inhibitors (ritonavir, ketoconazole, itraconazole, clarithromycin) | These drugs inhibit the liver enzyme that metabolizes tadalafil, leading to significantly increased tadalafil blood levels | Moderate-High — may require dose adjustment; ritonavir co-administration substantially increases tadalafil exposure |
| Alcohol | Additive vasodilation and blood pressure lowering; increased risk of dizziness, flushing, and hypotension | Moderate — limit alcohol consumption when using tadalafil |
| Antihypertensive medications (amlodipine, lisinopril, metoprolol, etc.) | Additive blood pressure lowering effect; may cause symptomatic hypotension | Low-Moderate — monitor blood pressure; usually manageable |
Who Should Not Take Tadalafil?
- Anyone currently using nitrate medications in any form (including nitroglycerin patches, sprays, tablets, or recreational "poppers") — this combination is absolutely contraindicated
- Patients with severe cardiovascular disease for whom sexual activity is inadvisable
- Patients who have had a stroke or heart attack within the past 90 days
- Patients with unstable angina or angina occurring during sexual intercourse
- Patients with severe liver disease (Child-Pugh Class C)
- Patients with severely low blood pressure (hypotension: below 90/50 mmHg) or uncontrolled high blood pressure
- Patients with a history of NAION (vision loss) associated with PDE5 inhibitor use
- Those with a known allergy to tadalafil or any component of the formulation
Frequently Asked Questions
Why is tadalafil called "the weekend pill"?
Tadalafil earned this nickname because its effects can last up to 36 hours — far longer than sildenafil (Viagra), which lasts 4–6 hours. This extended window means a single tablet taken on Friday evening can remain effective through the weekend, giving users significantly more flexibility in timing without needing to plan around medication. It can also be taken as a daily maintenance dose for continuous effect.
Why does tadalafil cause back pain when other ED drugs don't?
Back pain and muscle aches are a distinctive side effect of tadalafil that is not typically seen with sildenafil or vardenafil. This is because tadalafil weakly inhibits PDE11, an enzyme found in skeletal muscle and other tissues. PDE11 inhibition is thought to cause the muscular discomfort. These symptoms typically appear 12–24 hours after taking the medication and resolve on their own within 48 hours.
Can tadalafil be used for BPH and ED at the same time?
Yes. Tadalafil is the only PDE5 inhibitor approved to treat both erectile dysfunction and benign prostatic hyperplasia. Men who have both conditions may benefit from a single daily tablet that manages urinary symptoms and supports erectile function simultaneously. Your healthcare provider can determine if this combined approach is appropriate for your situation.
Is tadalafil safe with blood pressure medications?
Tadalafil can lower blood pressure, and combining it with antihypertensive medications may result in an additive blood pressure-lowering effect. This is generally manageable with monitoring, but alpha-blockers (drugs like doxazosin or tamsulosin, sometimes used for BPH) require particular care as they can cause significant drops in blood pressure when combined with tadalafil. Nitrate medications — an entirely different class — are an absolute contraindication, meaning they can never be combined with tadalafil under any circumstances.