[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Phosphodiesterase-5 inhibitors](https://durgical.com/en/pharmacology/classes/phosphodiesterase-5-inhibitors/) › Tadalafil # 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. Updated Nov 1, 2026 ## Quick facts **Group** [Phosphodiesterase-5 inhibitors](https://durgical.com/en/pharmacology/classes/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. On this page - The basics Mechanism of action - Indications - Adverse effects - Pharmacokinetics - Memory aid - Safety Contraindications - Key interactions - What is monitored - Administration and safety - Pregnancy and breastfeeding - Nursing care - Study Test yourself - Connections Connections ## Mechanism of action ✂**Phosphodiesterase type 5 (cGMP-specific phosphodiesterase)**Tadalafil ⓘ The figure shows tadalafil in the catalytic site of human PDE5 (crystal structure). **Target in 3D:** Phosphodiesterase type 5 (cGMP-specific phosphodiesterase). PDB structure 1UDU (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/1UDU) · Drag to rotate · pinch to zoom 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 →](https://durgical.com/en/conditions/erectile-dysfunction/) - Signs and symptoms of benign prostatic hyperplasia, with or without erectile dysfunction [Benign prostatic hyperplasia →](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/) - Pulmonary arterial hypertension, to improve exercise ability [Pulmonary hypertension and cor pulmonale →](https://durgical.com/en/conditions/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 ### Serious (rare, important) - Severe hypotension with nitrates or riociguat - Priapism - Sudden loss of vision (NAION) - Sudden decrease or loss of hearing ## 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 ## Memory aid TADAlafil = «the two-day tablet»: its long half-life means the nitrate warning lasts about two days, not one. ## 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. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/tadalafil/) [More Pharmacology questions →](https://durgical.com/en/practice/?f=pharmacology) ## Connections ## Related drugs 3 - [Sildenafil](https://durgical.com/en/pharmacology/sildenafil/) - [Tamsulosin](https://durgical.com/en/pharmacology/tamsulosin/) - [Doxazosin](https://durgical.com/en/pharmacology/doxazosin/) ## Related conditions 3 - [Erectile dysfunction](https://durgical.com/en/conditions/erectile-dysfunction/) - [Benign prostatic hyperplasia](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/) - [Pulmonary hypertension and cor pulmonale](https://durgical.com/en/conditions/pulmonary-hypertension-and-cor-pulmonale/) [← Back to the class: Phosphodiesterase-5 inhibitors](https://durgical.com/en/pharmacology/classes/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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3ad14d63-42e7-493f-b56c-e02a4fd139f7) (DailyMed (U.S. National Library of Medicine), 2026); [Tadalafil: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a604008.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=G04BE08) (WHO Collaborating Centre for Drug Statistics Methodology, 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/pharmacology/tadalafil/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/tadalafil/