[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Thiazide and thiazide-like diuretics](https://durgical.com/en/pharmacology/classes/thiazide-and-thiazide-like-diuretics/) › Chlortalidone [Pharmacology](https://durgical.com/en/pharmacology/) · [Thiazide and thiazide-like diuretics](https://durgical.com/en/pharmacology/classes/thiazide-and-thiazide-like-diuretics/) # Chlortalidone A long-acting thiazide-like diuretic for high blood pressure and oedema. Its effect lasts more than a day. Updated 2026-11-01 - Class: [Thiazide and thiazide-like diuretics](https://durgical.com/en/pharmacology/classes/thiazide-and-thiazide-like-diuretics/) - Transporter: Na⁺-Cl⁻ cotransporter (NCC) of the distal convoluted tubule - ATC code: C03BA04 Also called: Chlorthalidone ⇄**Na⁺-Cl⁻ cotransporter (NCC) of the distal convoluted tubule**Chlortalidone ⓘ The figure shows one of chlortalidone's two mirror-image forms (the S form) bound to the human NCC; the medicine is a mixture of both. **Target in 3D:** Na⁺-Cl⁻ cotransporter (NCC) of the distal convoluted tubule. PDB structure 8VPP (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/8VPP) · Drag to rotate · pinch to zoom ## Mechanism of action Chlortalidone is a sulfonamide that is not a true thiazide in structure but acts in the same way: it blocks the Na⁺-Cl⁻ cotransporter (NCC) of the distal convoluted tubule. More sodium and chloride are lost in the urine, potassium is lost in the collecting duct, and calcium reabsorption rises. Its long duration gives steady control of blood pressure. - Chlortalidone blocks NCC in the distal tubule - Na⁺ and Cl⁻ are lost in the urine; K⁺ follows downstream - Calcium reabsorption rises - Long action: steady lowering of blood pressure ## Pharmacokinetics **Absorption** Absorbed by mouth **Elimination** Mostly excreted unchanged by the kidneys **Onset and duration** Diuresis begins in about 2.6 hours and lasts up to 72 hours ## Indications - High blood pressure [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/) - Oedema from heart failure, cirrhosis, corticosteroids or kidney disease [Heart failure →](https://durgical.com/en/conditions/heart-failure/) ## Adverse effects ### Common - Hypokalaemia and hyponatraemia - High uric acid and gout - Higher blood glucose - Dizziness on standing - Photosensitivity and rash - Impotence ### Serious (rare, important) - Severe hypokalaemia or hyponatraemia - Hypercalcaemia (it can unmask hyperparathyroidism) - Pancreatitis and cholestatic jaundice (rare) - Blood disorders: agranulocytosis, thrombocytopenia, aplastic anaemia (rare) ## Contraindications - Anuria - Hypersensitivity to chlortalidone or other sulfonamide-derived drugs ## Key interactions **Lithium** Less lithium clearance and risk of toxicity **Digoxin** Hypokalaemia increases digoxin toxicity **Corticosteroids** More potassium loss **Insulin or oral antidiabetics** Blood glucose may rise, changing their needs ## What is monitored - Potassium, sodium and calcium - Kidney function - Blood pressure - Glucose and uric acid ## Nursing care - Before giving: blood pressure and potassium; report low values. - Watch for signs of low potassium or sodium: weakness, cramps, confusion. - In diabetes, check blood glucose more often at the start. - Teach: take it in the morning, rise slowly, protect the skin from the sun, report muscle cramps or joint pain (gout). ## Pregnancy and breastfeeding Not used for ordinary oedema in pregnancy; it crosses the placenta, with a risk of jaundice or low platelets in the newborn. ## Memory aid ChlorTALidone is the thiazide with the long TAIL: one dose and the effect drags on for days. ## Test yourself Think of the answer, then tap the question to see it. ## How does chlortalidone differ from hydrochlorothiazide? It is a thiazide-like sulfonamide with a different ring structure and a much longer duration of action, but it blocks the same NCC transporter. ## Which mineral does chlortalidone tend to raise in the blood? Calcium, because it increases calcium reabsorption in the distal tubule; marked hypercalcaemia can reveal hidden hyperparathyroidism. ## Can you name two contraindications of chlortalidone? Anuria and hypersensitivity to chlortalidone or other sulfonamide-derived drugs. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/chlortalidone/) ## Related drugs - [Hydrochlorothiazide](https://durgical.com/en/pharmacology/hydrochlorothiazide/) - [Indapamide](https://durgical.com/en/pharmacology/indapamide/) ## Related conditions - [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/) - [Heart failure](https://durgical.com/en/conditions/heart-failure/) [← Back to the class: Thiazide and thiazide-like diuretics](https://durgical.com/en/pharmacology/classes/thiazide-and-thiazide-like-diuretics/) 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 - CHLORTHALIDONE tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=36ef8d83-45f2-4873-b7cb-1be096d14d18) (DailyMed (U.S. National Library of Medicine), 2026); [Chlorthalidone: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a682342.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C03BA04) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [RCSB PDB - 8VPP: Phosphorylated human NCC in complex with chlorthalidone](https://www.rcsb.org/structure/8VPP) (RCSB Protein Data Bank, 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/chlortalidone/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/chlortalidone/