Drug Guide
Hydrochlorothiazide; Spironolactone
Classification
Therapeutic: Diuretic, Antihypertensive
Pharmacological: Combination potassium-sparing and thiazide diuretic
FDA Approved Indications
- Edema associated with congestive heart failure, hepatic cirrhosis, or renal disease; Hypertension
Mechanism of Action
Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule, increasing excretion of sodium, chloride, and water. Spironolactone antagonizes aldosterone receptors in the distal nephron, increasing sodium and water excretion while conserving potassium.
Dosage and Administration
Adult: Dosage varies based on condition; commonly, 25-50 mg once daily, titrated as needed.
Pediatric: Not typically used in pediatric patients; consult specific guidelines.
Geriatric: Start at lower end of dosing range; monitor for electrolyte imbalances and renal function.
Renal Impairment: Adjust dose according to severity of impairment; monitor renal function closely.
Hepatic Impairment: Use with caution; monitor closely due to altered drug metabolism.
Pharmacokinetics
Absorption: Well absorbed from gastrointestinal tract.
Distribution: Widely distributed in tissues; volume of distribution varies.
Metabolism: Hydrochlorothiazide minimally metabolized; spironolactone metabolized hepatically to active metabolites.
Excretion: Renal excretion via glomerular filtration and tubular secretion.
Half Life: Hydrochlorothiazide: 6-15 hours; Spironolactone: 1.5 hours (active metabolites: 13-16 hours).
Contraindications
- Anuria
- Serum potassium >5.0 mEq/L
- Severe renal impairment
- Overly suppressed bone marrow
Precautions
- Electrolyte imbalances (hyperkalemia, hyponatremia), dehydration, renal impairment, pregnancy (category D), lactation
Adverse Reactions - Common
- Hyperkalemia (Common)
- Hyponatremia (Common)
- Hypotension (Common)
- Dizziness (Common)
Adverse Reactions - Serious
- Serum potassium imbalance leading to cardiac arrhythmias (Serious)
- Dehydration/hypovolemia (Serious)
- Gynecomastia (spironolactone-related) (Less common)
- Nephrotoxicity (Less common)
Drug-Drug Interactions
- ACE inhibitors, ARBs (risk of hyperkalemia), NSAIDs (reduce antihypertensive effect, impair renal function), potassium supplements.
Drug-Food Interactions
- High potassium foods (risk of hyperkalemia).
Drug-Herb Interactions
- Herbal supplements containing potassium, diuretics, or laxatives.
Nursing Implications
Assessment: Monitor blood pressure, serum electrolytes, renal function, hydration status.
Diagnoses:
- Risk for electrolyte imbalance, risk for hypotension, risk for dehydration.
Implementation: Administer with meals to enhance absorption; monitor labs regularly; educate patient on diet and hydration.
Evaluation: Assess blood pressure, electrolyte levels, and kidney function periodically to evaluate therapy effectiveness.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Avoid excessive potassium-rich foods or potassium supplements unless directed.
- Report signs of hyperkalemia (muscle weakness, irregular heartbeat) or dehydration.
- Stand slowly to prevent dizziness.
Special Considerations
Black Box Warnings:
- Hyperkalemia can be fatal.
Genetic Factors: Certain genetic variations may impact drug response; consider genetic testing if indicated.
Lab Test Interference: May alter serum electrolyte and renal function tests.
Overdose Management
Signs/Symptoms: Severe hyperkalemia, dehydration, hypotension, electrolyte disturbances.
Treatment: Discontinue medication, administer potassium-binding resins, IV fluids, electrolyte correction, and supportive care.
Storage and Handling
Storage: Store at room temperature, away from moisture and heat.
Stability: Stable within expiration date when stored properly.