====== Hydrochlorothiazide (HCTZ®) ======<WRAP right 340px><WRAP infobox>| | {{ :cardio:diuretics:hydrochlorothiazide_structure.svg |}} |^ Hydrochlorothiazide || Brand Names | HCTZ® || Drug Class | [[cardio:diuretics:thiazide:start|Thiazide Diuretic]] || Primary Indications | [[cardio:hypertension:start|Hypertension]]; Mild edema || Blood Pressure Effect | ↓ BP (chronic) || Mortality Benefit | No (BP control) || Elimination | Renal || Black Box Warning | No || FDA Approval | 1959 |</WRAP></WRAP>===== 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.<WRAP clear></WRAP>----===== Mechanism of Action =====**Primary Molecular Target**  * Na-Cl cotransporter (NCC) in distal convoluted tubule**Segment Effects**  * ↓ NaCl reabsorption in DCT  * ↑ Ca2+ reabsorption  * Mild natriuresis**Net Physiologic Outcomes**  * ↓ blood pressure (long-term)  * Mild diuresis  * ↓ urinary calcium----===== Indications =====  * First-line hypertension (selected patients)  * Mild edema (HF, liver disease)  * Nephrolithiasis with hypercalciuria----<WRAP blackbox>===== Black Box Warning =====No black box warning.</WRAP>----<WRAP contra>===== Contraindications =====Absolute:  * AnuriaRelative / Caution:  * Gout  * Hyponatremia  * Hypokalemia  * Sulfonamide allergy (severe)</WRAP>----<WRAP details>===== Dosing =====Hypertension:  * 12.5–25 mg daily (typical)  * Max: 50 mg dailyEdema:  * 25–100 mg daily or divided</WRAP>----<WRAP details>===== Pharmacokinetics =====Absorption:  * OralBioavailability:  * ~60–70%Metabolism:  * Not significantHalf-life:  * ~6–15 hoursElimination:  * Renal</WRAP>----<WRAP details>===== Adverse Effects =====Common:  * Hypokalemia  * Hyponatremia  * Hyperuricemia  * HyperglycemiaSerious:  * Pancreatitis (rare)  * Severe hyponatremia</WRAP>----<WRAP details>===== Drug Interactions =====Increased risk:  * Lithium (↑ levels)  * NSAIDs (↓ effect)Avoid combination:  * Other QT-prolonging meds if severe hypokalemia</WRAP>----<WRAP monitoring>===== Monitoring =====Labs:  * Electrolytes (Na+, K+)  * Uric acid  * GlucoseVitals:  * Blood pressureClinical:  * Gout symptoms  * Orthostasis</WRAP>----<WRAP pearls>===== Clinical Pearls =====  * Chlorthalidone often preferred for longer duration  * Increases calcium reabsorption  * Can worsen gout and glucose control</WRAP>----===== Comparison Within Class =====Compared to other [[cardio:diuretics:thiazide:start|thiazide diuretics]]:  * Shorter half-life than chlorthalidone  * Commonly used in fixed-dose combos  * Less potent for resistant HTN----===== Related =====  * [[cardio:diuretics:thiazide:start|Thiazide Diuretics]]  * [[cardio:hypertension:start|Hypertension]]  * [[cardio:diuretics:start|Diuretics]]