Contraindications for Chlorthalidone
Chlorthalidone is absolutely contraindicated in patients with anuria and in those with known hypersensitivity to chlorthalidone or other sulfonamide-derived drugs. 1
Absolute Contraindications
- Anuria (complete cessation of urine production)
- Known hypersensitivity to chlorthalidone
- Hypersensitivity to other sulfonamide-derived drugs
Relative Contraindications and Cautions
Electrolyte Abnormalities
- Pre-existing hypokalemia: Chlorthalidone has a 2.72 times higher risk of causing hypokalemia compared to hydrochlorothiazide 2
- Pre-existing hyponatremia: Chlorthalidone increases the risk of hyponatremia by 31% compared to hydrochlorothiazide 2
- Severe electrolyte imbalances: Close monitoring required if therapy is initiated
Renal Considerations
- Advanced renal impairment: While not absolutely contraindicated in CKD, chlorthalidone requires careful monitoring as it increases risk of:
- eGFR <30 ml/min: Consider switching to a loop diuretic 3
Metabolic Concerns
- Gout or hyperuricemia: Chlorthalidone increases serum uric acid levels 4
- Diabetes mellitus: Increases risk of new-onset diabetes by 21% compared to hydrochlorothiazide 2
- Metabolic alkalosis: Risk increases due to volume contraction and chloride depletion 3
Other Considerations
- Severe hepatic disease: May precipitate hepatic encephalopathy
- Pregnancy: Use with caution as thiazides cross the placental barrier
- Concomitant use with certain medications:
- Caution with lithium (may increase lithium levels)
- Caution when combined with other medications that prolong QT interval
Monitoring Recommendations
When initiating chlorthalidone in patients without absolute contraindications:
Baseline measurements:
- Electrolytes (particularly potassium and sodium)
- Renal function
- Uric acid levels
- Glucose levels
Follow-up monitoring:
- Electrolytes and renal function within 4 weeks of initiating therapy 3
- Regular monitoring of glucose levels
- Monitor for signs of volume depletion and hypotension
Special Populations
- Elderly patients: Higher risk of adverse effects, particularly electrolyte abnormalities and orthostatic hypotension
- Patients with resistant hypertension: Despite risks, chlorthalidone may provide significant benefit in treatment-resistant hypertension even in advanced CKD (stage 4), with careful monitoring 5
- Patients with metabolic syndrome: While caution exists regarding thiazide diuretics in this population, chlorthalidone has shown effectiveness in reducing cardiovascular outcomes 6
While chlorthalidone has significant benefits for blood pressure control, its use requires careful consideration of contraindications and close monitoring for adverse effects, particularly electrolyte abnormalities and renal function changes.