POTASSIUM SPARING DIURETICS
- USES: Potassium sparing diuretics are used to treat congestive heart failure, fluid retention from liver failure, and hypertension. Spironolactone is used to prevent amphotericin B-related hypokalemia in cancer patients, and in the management of neonatal chronic lung disease. PHARMACOLOGY: Amiloride acts by blocking the sodium channel in the later portion of the nephron, distal tubule, and collecting duct. Triamterene inhibits the reabsorption of sodium ions in the exchange for potassium and hydrogen ions in the segment of the distal tubule under the control of adrenal mineralocorticoids. Eplerenone and spironolactone bind to aldosterone receptors in the distal tubules and collecting duct, preventing the binding of aldosterone to its receptor. Aldosterone acts at the kidney to cause sodium and water retention and potassium loss in the urine. TOXICOLOGY: Overdose may cause dehydration due to the diuretic effect. It can also cause electrolyte abnormalities, most commonly hyperkalemia. EPIDEMIOLOGY: Adverse effects during therapeutic use are relatively common. Potassium sparing diuretic overdose is rare and deaths have not been reported. MILD TO MODERATE TOXICITY: Nausea, vomiting, diarrhea, mild dehydration, and hyperkalemia may develop. SEVERE TOXICITY: Severe toxicity has not been reported, but severe dehydration (tachycardia, hypotension, and possibly mental status changes) and hyperkalemia (which may cause dysrhythmias) should be expected. Acute renal failure has been reported from triamterene deposition in the renal tubules after overdose. ADVERSE EFFECTS: Amiloride: Hyperkalemia, headache, paresthesia, depression, loss of libido, nausea, anorexia, diarrhea, vomiting, weakness, fatigue, muscle cramps. Eplerenone: Hyperkalemia, diarrhea, dizziness, fatigue, coughing. Spironolactone: Hyperkalemia, acidosis, cramping, diarrhea, drowsiness, lethargy, ataxia, gynecomastia, impotence, irregular menses. Triamterene: Hyperkalemia, diarrhea, nausea, vomiting, interstitial nephritis, blood dyscrasias, nephrolithiasis, photodermatitis.
Range of Toxicity:
POTASSIUM SPARING DIURETICS
- TOXICITY: No toxic dose for these medications has been established. An adult developed acute renal failure 3 days after ingesting 50 capsules of triamterene/hydrochlorothiazide. Two infants, ages 10 and 12 months, ingested up to 60 spironolactone tablets, with asymptomatic hyperkalemia as the only effect noted. THERAPEUTIC DOSE: AMILORIDE: ADULT: 5 to 20 mg/day orally; PEDIATRIC: 6 to 20 kg in body weight: 0.625 mg/kg/day orally. EPLERENONE: ADULT: 25 to 50 mg orally once or twice daily; PEDIATRIC: Safety and efficacy not established. SPIRONOLACTONE: ADULT: 25 to 100 mg/day orally in single or divided doses; PEDIATRIC: 1 to 3 mg/kg/day orally in 2 to 4 divided doses or once daily; MAX 200 mg/day. TRIAMTERENE: ADULT: 100 mg orally twice daily; MAX 300 mg/day; PEDIATRIC: Edema: 1 to 4 mg/kg/day orally in 2 divided doses. Hypertension: initially, 1 to 2 mg/kg/day orally in two divided doses; MAX 3 to 4 mg/kg/day, up to 300 mg/day.
POTASSIUM SPARING DIURETICS
- Support: MANAGEMENT OF MILD TO MODERATE TOXICITY: Serious toxicity is not expected after ingestion. Most patients will remain asymptomatic or have a mild diuresis. Oral rehydration and monitoring for hyperkalemia is sufficient in most cases. MANAGEMENT OF SEVERE TOXICITY: Correct dehydration with intravenous fluids. There is a theoretical risk of hyperkalemia following overdose. Hyperkalemia is treated in the usual fashion: administer calcium chloride for dysrhythmias or wide complex rhythms. Sodium bicarbonate, insulin, glucose, and cationic exchange resins (eg, sodium polystyrene sulfonate) may also be used. Dialysis may be required for patients with impaired renal function.
- Decontamination: PREHOSPITAL: Gastrointestinal decontamination is not indicated. HOSPITAL: Gastrointestinal decontamination should not be routinely performed following potassium sparing diuretic ingestion. Activated charcoal may be considered after extremely large ingestions or if more toxic coingestants are involved and the patient has presented early after the ingestion.
- Airway management: Airway compromise is not expected following potassium sparing diuretic ingestion.
- Antidote: None
- Monitoring of patient: Monitor serum electrolytes and ECG after overdose. Drug concentrations are not routinely available and are not used clinically to guide management following overdose.
- Enhanced elimination procedure: As significant toxicity is not expected, there is no role for enhanced elimination following ingestion. Dialysis is ineffective in removing spironolactone, but may increase the clearance of triamterene.
- Patient disposition: HOME CRITERIA: Asymptomatic patients with small, inadvertent ingestions and normal renal function can be monitored at home. OBSERVATION CRITERIA: Patients with large or deliberate ingestions or impaired renal function should be monitored for fluid status and serum electrolytes changes (particularly sodium and potassium). Monitor vital signs and ECG in symptomatic patients and those with significant electrolyte abnormalities. ADMISSION CRITERIA: Admit patients with severe electrolyte abnormalities, dehydration, or impaired renal function. CONSULT CRITERIA: Consult a poison center or medical toxicologist for assistance in managing patients with severe toxicity or in whom the diagnosis is not clear.