Chlorthalidone

# Chlorthalidone ## Overview - **Classification**: Thiazide-like Diuretic - **Mechanism**: Inhibits Na+/Cl- reabsorption in the distal convoluted tubule, increasing excretion of Na+, Cl-, water, and K+. ## Primary Indications 1. **Hypertension** - Management of high blood pressure, often first-line. 2. **Edema** - Treatment of fluid retention associated with conditions like CHF, renal dysfunction, or hepatic cirrhosis. ## Adult Dosing ### Standard Dosing **Hypertension** - **Dose**: Initial **12.5 mg** to **25 mg** - **Frequency**: Once daily - **Route**: Oral - **Maximum dose**: **50 mg** daily (higher doses rarely provide additional BP lowering but increase side effects). **Edema** - **Dose**: Initial **25 mg** to **100 mg** - **Frequency**: Once daily or intermittent (e.g., 3-4 times/week) - **Route**: Oral - **Maximum dose**: Up to **200 mg** daily in severe cases, but rarely needed. ### Dose Adjustments - **Renal Impairment**: - CrCl <30 mL/min: Generally **not effective** as a diuretic. Use with caution or avoid. - CrCl 30-50 mL/min: Use with caution, consider lower starting doses (e.g., **12.5 mg**). - **Hepatic Impairment**: Use with caution due to risk of electrolyte imbalance and hepatic coma. - **Elderly Patients**: Start with lower doses (e.g., **12.5 mg**) due to increased sensitivity to diuretic effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Generally not recommended**: Limited data and experience. - **Special Notes**: Consult a pediatric nephrologist or specialist if diuretic is required. ### Infants (1-12 months) - **Generally not recommended**: Limited data and experience. - **Special Notes**: Consult a pediatric nephrologist or specialist if diuretic is required. ### Children (1-12 years) - **Dose**: **0.2 mg/kg** to **0.5 mg/kg** - **Frequency**: Once daily - **Maximum**: **50 mg** daily for hypertension; **100 mg** daily for edema. - **Special Notes**: Start low and titrate slowly. Closely monitor electrolytes. ### Adolescents (13-18 years) - **Dose**: Initial **12.5 mg** to **25 mg** - **Frequency**: Once daily - **Maximum**: **50 mg** daily for hypertension; **100 mg** daily for edema. - **Special Notes**: Dosing approaches adult recommendations, adjusted for weight and response. ## Safety Information ### Contraindications - **Absolute**: Anuria - **Absolute**: Hypersensitivity to chlorthalidone or sulfonamide-derived drugs. - **Relative**: Severe renal impairment (CrCl <30 mL/min) due to lack of efficacy. ### Common Adverse Effects - **Very Common (>10%)**: Hypokalemia, hyperuricemia, hyperglycemia, hypomagnesemia. - **Common (1-10%)**: Dizziness, headache, nausea, muscle cramps, impotence. - **Serious but Rare**: Agranulocytosis, aplastic anemia, pancreatitis, Stevens-Johnson syndrome. ### Key Drug Interactions - **NSAIDs**: May reduce diuretic and antihypertensive effects; monitor BP. - **Lithium**: Reduces renal clearance of lithium, increasing toxicity risk; monitor lithium levels. - **Digoxin**: Hypokalemia increases risk of digoxin toxicity; monitor K+ and digoxin levels. - **Corticosteroids**: Increased risk of hypokalemia; monitor K+. - **Antidiabetic agents**: May increase blood glucose; monitor glucose, adjust antidiabetic dose. ## Monitoring & Follow-up - **Before Treatment**: Baseline serum electrolytes (Na, K, Mg, Ca), uric acid, glucose, renal function (BUN, Cr). - **During Treatment**: Electrolytes (especially K, Na) within 1-2 weeks, then monthly for initial months, then every 3-6 months. Periodically monitor renal function. - **Clinical Signs**: Watch for signs of dehydration, muscle weakness, cramps, dizziness (suggestive of electrolyte imbalance). ## Clinical Pearls - 💡 **Tip 1**: Administer in the morning to prevent nocturia and sleep disturbance. - 💡 **Tip 2**: Often preferred over hydrochlorothiazide for hypertension due to longer half-life and robust evidence for cardiovascular benefits. - 💡 **Tip 3**: Counsel patients on symptoms of hypokalemia (e.g., fatigue, muscle weakness, cramps). - 💡 **Tip 4**: Consider potassium supplementation or a potassium-sparing diuretic if hypokalemia is significant. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.