Tadalafil
Phosphodiesterase-5 inhibitors
Phosphodiesterase-5 inhibitors
A long-acting PDE5 inhibitor for erectile dysfunction, the urinary symptoms of an enlarged prostate and pulmonary arterial hypertension.
Quick facts
- Group
- Phosphodiesterase-5 inhibitors
- Target
- Phosphodiesterase type 5 (cGMP-specific phosphodiesterase)
- Used for
- Erectile dysfunction · Signs and symptoms
- Key effects
- Headache · Dyspepsia · Back pain and myalgia
- Monitor
- Blood pressure · Kidney function
- ATC
- G04BE08
No doses: the clinician sets them by the current guideline.
Mechanism of action
The figure shows tadalafil in the catalytic site of human PDE5 (crystal structure).
Tadalafil inhibits PDE5 and so protects cyclic GMP made in response to nitric oxide. In the corpus cavernosum this eases erection during sexual stimulation; in the prostate, bladder and their vessels it relaxes smooth muscle and improves urinary symptoms of benign prostatic hyperplasia; in the lungs it relaxes the pulmonary arteries. It differs from sildenafil mainly in its long half-life and in weak inhibition of PDE11 rather than PDE6, so colour vision changes are rare.
- Nitric oxide activates guanylyl cyclase and cGMP is made
- Tadalafil blocks PDE5 for many hours
- cGMP relaxes smooth muscle in penis, prostate and lung vessels
- Erection and urine flow improve; pulmonary resistance falls
Indications
- Erectile dysfunction Erectile dysfunction →
- Signs and symptoms of benign prostatic hyperplasia, with or without erectile dysfunction Benign prostatic hyperplasia →
- Pulmonary arterial hypertension, to improve exercise ability Pulmonary hypertension and cor pulmonale →
Adverse effects
Common
- Headache
- Dyspepsia
- Back pain and myalgia, often a day after a dose
- Nasal congestion and flushing
- Limb pain
Contraindications
- Use of organic nitrates in any form
- Use of riociguat or another guanylate cyclase stimulator
- Serious hypersensitivity to tadalafil
- Caution when sexual activity is inadvisable because of heart disease
Key interactions
- Nitrates
- Severe hypotension; if a nitrate becomes life-saving, the label asks for at least 48 hours after the last tadalafil dose and close monitoring
- Riociguat
- Additive hypotension; contraindicated
- Alpha blockers, antihypertensives and substantial amounts of alcohol
- Additive fall in blood pressure; the combination with alpha blockers is not recommended for prostate symptoms
- Strong CYP3A4 inhibitors (ketoconazole, ritonavir)
- Higher tadalafil exposure
- CYP3A4 inducers (rifampicin)
- Lower tadalafil levels
What is monitored
- Blood pressure, especially with alpha blockers or antihypertensives
- Kidney function, because exposure rises in kidney disease
- Vision and hearing complaints
- Urinary symptoms in prostate treatment; other urological causes are excluded first
Administration and safety
- Oral tablets, taken with or without food
- Used on demand or once daily depending on the indication
- Products for pulmonary hypertension and for erectile dysfunction contain the same drug and are not taken together
Pregnancy and breastfeeding
Animal studies at high exposures showed no developmental harm, and there are no human data; for pulmonary hypertension in pregnancy the specialist team decides.
Nursing care
- Record any nitrate use and teach the patient to tell emergency staff that he takes tadalafil
- Teach that its effect lasts much longer than sildenafil's, so the nitrate warning lasts longer too
- Check blood pressure and ask about dizziness when combined with alpha blockers
- Teach the warning signs: an erection lasting more than four hours, sudden loss of vision or hearing
Pharmacokinetics
- Absorption
- Oral; food does not affect absorption
- Distribution
- Distributes into tissues; highly bound to plasma proteins
- Metabolism
- Liver, mainly CYP3A4
- Elimination
- As metabolites, mainly in faeces and less in urine
- Half-life
- About 17.5 hours in healthy adults
- Onset and duration
- Peak levels about two hours after a dose; effect lasts up to about a day and a half
Test yourself
Think of the answer, then tap the question to see it.
What is the main pharmacokinetic difference between tadalafil and sildenafil?
Tadalafil has a much longer half-life (about 17.5 hours versus about 4 hours), so its effect and interaction window last longer.
Which urological condition is treated with tadalafil but not with sildenafil?
Urinary symptoms of benign prostatic hyperplasia.
Why are colour vision changes rarer with tadalafil than with sildenafil?
Tadalafil inhibits PDE6 of the retina very little; its off-target enzyme is mainly PDE11.
Connections
← Back to the class: Phosphodiesterase-5 inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - TADALAFIL tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Tadalafil: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.