Hydrochlorothiazide

Hydrochlorothiazide is a thiazide diuretic used to treat hypertension and edema. It works by removing excess water and sodium from the body through urine, which helps lower blood pressure. It may be used alone or in combination with other medicines. Thiazide diuretics work by inhibiting Na+/Cl- reabsorption from the distal convoluted tubules, increasing excretion of sodium and water.

• Hypertension (high blood pressure)
• Edema associated with congestive heart failure
• Edema associated with hepatic cirrhosis
• Edema associated with premenstrual tension
• Edema due to renal dysfunction (nephrotic syndrome, acute glomerulonephritis, chronic renal failure)

Adult Dose (Oral):

• Hypertension: Initial: 12.5 mg; may increase to 25-50 mg daily as needed
• Edema: 25-100 mg daily in 1-2 divided doses or intermittently on alternate days or 3-5 days a week
• Elderly: 12.5-25 mg once daily; titrate in increments of 12.5 mg

Child Dose (Oral):

• Hypertension & Edema (2-12 years): 1-2 mg/kg/day in 1-2 divided doses; Max: 100 mg/day
• Infants under 6 months: up to 3 mg/kg daily

Renal Dose: CrCl 10 mL/min: No dose adjustment; not effective with CrCl <30 mL/min unless combined with loop diuretic

Common Side Effects:

• Headache
• Nausea
• Increased blood uric acid
• Decreased potassium level in blood
• Glucose intolerance
• Altered blood lipid level

Gastrointestinal: Anorexia, gastric irritation, vomiting, diarrhea, constipation, pancreatitis

CNS: Dizziness, vertigo, paresthesia, yellow vision

Hematological: Leukopenia, thrombocytopenia

Cardiovascular: Hypotension (including orthostatic)

Precautions:

• Hydrochlorothiazide may decrease alertness, affect vision or make you feel sleepy and dizzy; do not drive if these symptoms occur
• Take in the morning with breakfast to avoid getting up at night to urinate
• Avoid alcohol (may increase dizziness)
• May cause sudden drop of sodium level; avoid low sodium diet
• Monitor blood pressure; notify doctor if it does not lower down
• Notify doctor if dizziness, tiredness, or muscle weakness persists
• Monitor for signs of fluid and electrolyte imbalance
• Caution in kidney or liver disease

Contraindications:

• Anuria
• Hypersensitivity to sulfonamide-derived drugs
• Severe renal impairment (CrCl <30 mL/min)
• Severe hepatic failure
• Addison's disease
• Hypercalcemia
• Concurrent lithium therapy

Drug Interactions:

• Alcohol, Barbiturates, Narcotics: May potentiate orthostatic hypotension
• Antidiabetic drugs: Dosage adjustment may be required
• Other antihypertensives: Additive effect
• Corticosteroids, ACTH: May intensify electrolyte depletion (especially hypokalemia)
• NSAIDs: May attenuate diuretic and antihypertensive effects
• Lithium: Increased toxicity
• Cholestyramine & Colestipol: Reduced absorption of hydrochlorothiazide

Food Interactions: Hydrochlorothiazide may cause excessive drowsiness with alcohol.

Use in Pregnancy: May be unsafe; thiazides cross the placental barrier and appear in cord blood; may cause fetal or neonatal jaundice, thrombocytopenia; routine use in healthy pregnant women is not recommended.

Use in Lactation: Thiazides appear in breast milk; if drug use is deemed essential, patient should stop breastfeeding.

Pediatric Use: Initial dose: 1-2 mg/kg in 2 divided doses; infants under 6 months: up to 3 mg/kg daily.

Geriatric Use: In some patients, especially the elderly, an initial dose of 12.5 mg daily may be sufficient.

Renal Impairment: Thiazide diuretics become ineffective when creatinine clearance falls below 30 mL/min; caution in severe kidney disease; dose adjustment may be needed.

Hepatic Impairment: Caution in liver disease; minor alterations of fluid and electrolyte balance may precipitate hepatic coma; dose adjustment may be needed.

Overdose: Electrolyte depletion (hypokalemia, hypochloremia, hyponatremia) and dehydration from excessive diuresis; hypokalemia may accentuate cardiac arrhythmias if digitalis also given; symptomatic and supportive measures.