Chlorthalidone
THALITONE
Pronunciation: klor-THAL-i-doen
“Cooler thiazide, lid on”
Bananas dispersing → ↓ serum potassium
What it isThiazide-like NCC inhibitor; hypertension and edema.
Why this oneIts longer action and stronger outcomes evidence distinguish it from hydrochlorothiazide.
What limits itHyponatremia and hypokalemia are more pronounced than with hydrochlorothiazide; monitor electrolytes and renal function.
FDA-approved for
- hypertension/edema (~1960)
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Hypertension | Adults | 25 mg QD (morning) | 25–50 mg QD | 100 mg/day (>100 no added benefit) |
| Edema | Adults | 50–100 mg QD or 100 mg every other day | 50–200 mg QD or alternate days | 200 mg/day |
Titration Increase after a suitable trial if response insufficient
Renal Undefined
Hepatic Undefined
Instructions
- Single dose in the morning with food
- Divided daily doses are unnecessary
- Maintenance doses may be lower than initial; titrate to response
Available strengths
- tab 12.5, 15, 25, 50 mg
Contraindications
- Anuria
- Hypersensitivity to sulfonamide-derived drugs
Cautions
- Electrolyte imbalance (hypokalemia, hyponatremia); monitor serum electrolytes
- Increases serum uric acid and blood glucose (dose-related)
- Orthostatic hypotension, aggravated by alcohol/barbiturates/narcotics
- Idiosyncratic reactions, photosensitivity, hypersensitivity
Adverse reactions
- GI: anorexia, gastric irritation, nausea, vomiting, cramping, pancreatitis, cholestatic jaundice
- CNS: dizziness, vertigo, paresthesias, headache
- Hematologic: leukopenia, agranulocytosis, thrombocytopenia, aplastic anemia
- Metabolic: hyperglycemia, glycosuria, hyperuricemia; impotence
Pregnancy Category B; use only if clearly needed — thiazides cross placenta (risk fetal/neonatal jaundice, thrombocytopenia)
Lactation Undefined
Cost
Generic entry1982
NO BOXED WARNINGS
Principal riskHyponatremia and hypokalemia; longer-acting than hydrochlorothiazide
Classes and tags
Clinical profile
Legacy pregnancy categoryC
Defining liabilityHyponatremia, hypokalemia and substantial elevation of lithium concentrations.
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