====== Hydrochlorothiazide (HCTZ®) ======
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|^ Hydrochlorothiazide || Brand Names | HCTZ® || Drug Class | Thiazide Diuretic || Primary Indications | Hypertension; Mild edema || Blood Pressure Effect | ↓ BP (chronic) || Mortality Benefit | No (BP control) || Elimination | Renal || Black Box Warning | No || FDA Approval | 1959 |
===== Overview =====Hydrochlorothiazide is a thiazide diuretic that inhibits the Na-Cl cotransporter in the distal convoluted tubule. It lowers blood pressure chronically via reduced peripheral vascular resistance and treats mild edema.
—-===== Mechanism of Action =====Primary Molecular Target * Na-Cl cotransporter (NCC) in distal convoluted tubuleSegment Effects * ↓ NaCl reabsorption in DCT * ↑ Ca2+ reabsorption * Mild natriuresisNet Physiologic Outcomes * ↓ blood pressure (long-term) * Mild diuresis * ↓ urinary calcium—-===== Indications ===== * First-line hypertension (selected patients) * Mild edema (HF, liver disease) * Nephrolithiasis with hypercalciuria—-
===== Black Box Warning =====No black box warning.
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===== Contraindications =====Absolute: * AnuriaRelative / Caution: * Gout * Hyponatremia * Hypokalemia * Sulfonamide allergy (severe)
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===== Dosing =====Hypertension: * 12.5–25 mg daily (typical) * Max: 50 mg dailyEdema: * 25–100 mg daily or divided
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===== Pharmacokinetics =====Absorption: * OralBioavailability: * ~60–70%Metabolism: * Not significantHalf-life: * ~6–15 hoursElimination: * Renal
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===== Adverse Effects =====Common: * Hypokalemia * Hyponatremia * Hyperuricemia * HyperglycemiaSerious: * Pancreatitis (rare) * Severe hyponatremia
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===== Drug Interactions =====Increased risk: * Lithium (↑ levels) * NSAIDs (↓ effect)Avoid combination: * Other QT-prolonging meds if severe hypokalemia
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===== Monitoring =====Labs: * Electrolytes (Na+, K+) * Uric acid * GlucoseVitals: * Blood pressureClinical: * Gout symptoms * Orthostasis
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===== Clinical Pearls ===== * Chlorthalidone often preferred for longer duration * Increases calcium reabsorption * Can worsen gout and glucose control
—-===== Comparison Within Class =====Compared to other thiazide diuretics: * Shorter half-life than chlorthalidone * Commonly used in fixed-dose combos * Less potent for resistant HTN—-===== Related ===== * Thiazide Diuretics * Hypertension * Diuretics