Triamterene is a potassium-sparing diuretic widely used in the therapy of edema. Triamterene has been linked to rare cases of clinically apparent drug induced liver disease.
Triamterene (trye am' ter een) is an inhibitor of renal epithelial sodium channels in the late distal tubule and collecting ducts of the kidney. As a result, triamterene promotes a mild sodium diuresis, but maintains body potassium levels. Triamterene is used largely in therapy of edema and can be safely used in patients with cirrhosis. Because of its potassium-sparing actions, triamterene is also used in combination with thiazide or loop diuretics in an attempt to prevent hypokalemia. Triamterene was approved for use in the United States in 1964 and continues to be widely used with more than 20 million prescriptions filled yearly. Triamterene is available in tablets and capsules of 50 and 100 mg in generic forms and under the brand name of Dyrenium. The typical dose of triamterene is 50 to 200 mg daily in one or two divided doses. Triamterene is also available in fixed dose combinations with hydrochlorothiazide (Maxide, Dyazide and generically). The major side effects of triamterene are dizziness, fatigue, headache, dry mouth, hyperkalemia and dehydration.
Triamterene therapy has been associated with rare instances of idiosyncratic, clinically apparent liver injury which have invariably been mild and anicteric. The liver injury typically arises after 4 to 12 weeks of therapy and the pattern of serum enzyme elevations is usually hepatocellular or mixed. Fever is a prominent symptom and the reaction is often more typical of drug-fever than hepatotoxicity (Case 1). Rash and eosinophilia can occur, but are usually not prominent. Autoantibodies are rare. All published cases of triamterene associated liver injury have been self-limited in course and resolved rapidly upon withdrawal.
Likelihood score: D (possible rare cause of clinically apparent liver injury).
Mechanism of Injury
The mechanism of triamterene hepatic injury is unknown, but it likely to be due to hypersensitivity.
Outcome and Management
Most instances of triamterene associated liver injury have been mild and rapidly reversible upon drug withdrawal. Rapid recurrence upon rechallenge has been reported. There is no evidence of cross reactivity to the hepatic injury with other diuretics.
|Medication:||Triamterene (100 mg daily)|
|Severity:||Mild (enzyme elevations without jaundice)|
|Latency:||1 month initially, 1 day on rechallenge|
|DRUG||CAS REGISTRY NUMBER||MOLECULAR FORMULA||STRUCTURE|
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