Chlortalidone
A long-acting thiazide-like diuretic used for high blood pressure and edema.
Also called chlorthalidone (US name).
Drug card
- Class
- Thiazide diuretic
- How it works
- Blocking salt reabsorption in the distal tubule, so more salt and water leave
- Used for
- High blood pressure
- Edema, including from heart failure
- Known for
- Low potassium (hypokalemia), dose-related
- Raised uric acid (hyperuricemia), dose-related
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does chlortalidone work?
Chlortalidone is a thiazide-like sulfonamide that lacks the benzothiadiazine ring. It blocks sodium and chloride reabsorption in the early distal convoluted tubule. It binds tightly to carbonic anhydrase in red blood cells, and its half-life of 40 to 60 hours is far longer than that of hydrochlorothiazide.
Like other thiazide and thiazide-like diuretics: They block the sodium-chloride cotransporter in the distal convoluted tubule, so more sodium, chloride and water leave in the urine, along with potassium and magnesium, while calcium and uric acid are held back. The lasting fall in blood pressure comes mainly from lower peripheral resistance, by a mechanism that is not fully understood.
Uses
What is chlortalidone used for?
- High blood pressure
- Edema, including from heart failure
Side effects
Side effects of chlortalidone
- Low potassium (hypokalemia), dose-relatedKnown forSerious
- Raised uric acid (hyperuricemia), dose-relatedKnown for
- Low sodium (hyponatremia)Serious
- Low magnesium (hypomagnesemia)
- Gout attacks
- Raised blood sugar (hyperglycemia)
- Raised cholesterol and triglycerides
- Raised calcium (hypercalcemia)
- Acute kidney injury from fluid lossSerious
- Dizziness on standing (orthostatic hypotension)
- Sensitivity to sunlight (photosensitivity)
- PancreatitisSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Contraindicated in anuria and in allergy to sulfonamide-derived drugs.
- Low magnesium can make low potassium hard to correct, so both are checked.
- Chronic kidney disease, heart failure or low fluid volume raise the risk of acute kidney injury, so kidney function is checked.
- Lupus can flare or appear.
Good to know: Chlortalidone is the INN; the US name is chlorthalidone. Its half-life of 40 to 60 hours is much longer than hydrochlorothiazide's.
Remember it
A way to remember it
GLUC
- G
- Glucose up
- L
- Lipids up
- U
- Uric acid up
- C
- Calcium up
Think 'hyper-GLUC': thiazides raise blood glucose, lipids, uric acid and calcium, while potassium, sodium and magnesium fall.
A mnemonic widely used in teaching
Its class
Thiazide and thiazide-like diuretics
Other thiazide and thiazide-like diuretics with a card:
Easily mixed up with loop diuretics and mineralocorticoid receptor antagonists.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood pressure
Chlortalidone is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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