hydrochlorothiazide (Microzide, HydroDiuril, Hydro, Esidrix, HCTZ, Oretic)
Classes: Diuretics, Thiazide
Dosing and uses of Microzide, HydroDiuril (hydrochlorothiazide)
Adult dosage forms and strengths
tablet/capsule
- 12.5mg
- 25mg
- 50mg
Hypertension
12.5-50 mg PO once daily
Edema
25-100 mg PO once daily or twiced daily; not to exceed 200 mg/day
Hypertension in Heart Failure (Off-label)
25 mg PO qDay or twice daily; not to exceed 200 mg/day
Mild Fluid Retention in Heart Failure (Off-label)
25 mg PO qDay or twice daily; not to exceed 200 mg/day
Dosing Considerations
Overdose management
- Normal saline may be used for volume replacement
- Dopamine or norepinephrine may be used to treat hypotension
- If dysrhythmia due to decreased potassium or magnesium is suspected, replace aggressively
- If no symptoms are noted after 6 hours, discontinue treatment
Dosing Modifications
Renal impairment
- CrCl <10 mL/min: Avoid use
- CrCl ≥10 mL/min: Dose adjustment not necessary; not effective with CrCl <30 mL/min unless used in combination with loop diuretic
Pediatric dosage forms and strengths
tablet/capsule
- 12.5mg
- 25mg
- 50mg
Hypertension
<6 months: 1-3 mg/kg/day PO divided q12hr; not to exceed 37.5 mg/day
6 months-2 years: 1-2 mg/kg/day PO in single daily dose or divided twice daily; not to exceed 37.5 mg/day
2-12 years: 1-3 mg/kg/day; not to exceed 3 mg/kg/day (100 mg/day)
Edema
<6 months: 1-3 mg/kg/day PO divided q12hr; not to exceed 37.5 mg/day
6 months-2 years: 1-3 mg/kg/day PO in single daily dose or divided twice daily; not to exceed 37.5 mg/day
2-12 years: 1-3 mg/kg/day; not to exceed 3 mg/kg/day (100 mg/day)
Geriatric dosage forms and strengths
Increased hypotension and side effects in elderly
Potential for electrolyte imbalance in elderly; monitor serum electrolytes
Diuresis
12.5-25 mg/day PO; titrated in increments of 12.5 mg/day
Increased electrolyte disturbances are seen with dosages >50 mg/day
Microzide, HydroDiuril (hydrochlorothiazide) adverse (side) effects
Frequency not defined
Anaphylaxis
Anorexia
Confusion
Disorder of hematopoietic structure
Dizziness
Epigastric distress
Fatigue
Headache
Hepatotoxicity
Hypercalcemia
Hypercholesterolemia
Hyperglycemia
Hyperlipidemia
Hyperuricemia
Hypokalemia
Hypomagnesemia
Hypotension
Interstitial nephritis
Metabolic acidosis
Muscle weakness or cramps
Nausea
Necrotizing angiitis
Pancreatitis
Phototoxicity
Pneumonitis
Pulmonary edema
Purpura
Rash
Respiratory distress
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Vertigo
Vomiting
Xanthopsia
Warnings
Contraindications
Documented hypersensitivity to hydrochlorothiazide or sulfonamides
Anuria
Cautions
Use with caution in diabetes mellitus, fluid or electrolyte imbalance, hypercholesterolemia, hyperuricemia or gout, hypercalcemia, hypotension, systemic lupus erythematosus, liver or renal disease, hypokalemia, parathyroid disease
May aggravate digitalis toxicity
Sensitivity reactions may occur with or without history of allergy or asthma
Avoid concurrent use with lithium (reduction of lithium dosage by 50% may be necessary)
Risk of male sexual dysfunction
Causes systemic lupus exacerbation or activation
Azotemia may occur with severe renal disease
Acute transient myopia and acute angle-closure glaucoma have been reported, particularly with history of sulfonamide or penicillin allergy (hydrochlorothiazide is sulfonamide)
FDA-approved product labeling for many medications have included a broad contraindication in patients with a prior allregic reaction to sulfonamides; however, recent studies have suggested that crossreactivity between antibiotic sulfonamides and nonantibiotic sulfonamides is unlikely to occur
Photosensitization may occur
Electrolyte disturbances (eg, hypokalemia, hyponatremia, hypochloremic alkalosis) may occur
Pregnancy and lactation
Pregnancy category: B
Lactation: Drug excreted in breast milk; use with caution (American Academy of Pediatrics states that it is "compatible with nursing")
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Microzide, HydroDiuril (hydrochlorothiazide)
Mechanism of action
Thiazide diuretic; inhibits sodium reabsorption in distal renal tubules, resulting in increased excretion of water and of sodium, potassium, and hydrogen ions
Absorption
Onset: Diuresis, ~2 hr; hypertension, 3-4 days
Peak plasma time: 1-2.5 hr
Peak effect: Diuresis, 4-6 hr
Bioavailability: 65-75%
Distribution
Protein bound: 40-68%
Vd: 3.6-7.8 L/kg
Metabolism
Minimally metabolized
Elimination
Half-life: 5.6-14.8 hr
Dialyzable: Hemodialysis, no
Excretion: Urine
