Hydrochlorothiazide
Microzide | HydroDIURIL
Overview
Thiazide diuretic used to treat hypertension and edema by reducing sodium and water reabsorption in the kidneys.
Indications
- Hypertension
- Edema (heart failure, hepatic cirrhosis)
- Nephrolithiasis (calcium stones)
- Diabetes insipidus (nephrogenic)
Contraindications
- Anuria
- Sulfonamide hypersensitivity
Classification
Mechanism of Action
Inhibits sodium-chloride cotransporter in the distal convoluted tubule, increasing sodium and water excretion.
Pharmacodynamics
Reduces blood volume and cardiac output initially, then decreases peripheral vascular resistance with chronic use.
Pharmacokinetics
- Absorption
- Rapidly absorbed from GI tract. Onset 2 hours, peak 4 hours.
- Distribution
- Crosses placenta. Distributed to breast milk.
- Metabolism
- Not metabolized. Excreted unchanged.
- Excretion
- Renal (>95% unchanged within 24 hours).
- Half-life
- 6-15 hours
- Bioavailability
- 65-75%
- Protein Binding
- 40-68%
Dosage
Typical dosage: 12.5-50mg once daily
Available Forms
- Tablet
- Capsule
Side Effects
Common
- Hypokalemia
- Hyperuricemia
- Dizziness
- Increased urination
Serious
- Severe electrolyte imbalance
- Acute renal failure
- Pancreatitis
Rare
- Stevens-Johnson syndrome
- Aplastic anemia
Drug Interactions
Thiazides reduce lithium clearance, increasing toxicity risk. Monitor lithium levels closely.
HCTZ-induced hypokalemia increases risk of digoxin toxicity.
Warnings
Pregnancy
Category B
Toxicity
LD50 >10 g/kg (oral, rat)
Overdose
Symptoms: electrolyte depletion, dehydration, hypotension. Treatment: IV fluids, electrolyte replacement.
References
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