New Therapy Update

Abstract

Dyrenium® (triamterene, GlaxoSmithKline) is a potassium-sparing diuretic used in the treatment of edema associated with congestive heart failure, liver cirrhosis, nephrotic syndrome, and use of steroids or secondary hyperaldosteronism. The drug is also used in combination with other diuretics in the treatment of hypokalemia and hypertension. Triamterene inhibits the reabsorption of sodium in exchange for potassium and hydrogen in the distal tubule. The action of the drug is under the control of mineralocorticoid (aldosterone) activity. The more sodium reaching the distal tubule, the stronger the diuretic effect and potassium conservation. After oral administration, the drug is rapidly absorbed. The onset of action is in 2–4 hours, and peak effect occurs after several days of therapy. The duration of action is 7–9 hours. 80% of the drug is metabolized in the liver and 50% is excreted in the urine. The plasma half-life is 1.5–2.5 hours. The drug is contraindicated in patients with anuria or severe, progressive renal disease and diabetic nephropathy. It should not be given to patients with severe hepatic dysfunction. It should not be used in patients with elevated potassium levels or patients already taking another potassium-sparing diuretic. During triamterene administration, blood pressure, urine output, weight, and serum electrolytes should be monitored. Arrhythmias, orthostatic hypotension, and angina are the most common adverse cardiac reactions. Dehydration, fatigue, muscle cramps, nausea, and diarrhea are other reported adverse effects. The drug should not be used with other potassium-sparing diuretics, such as spironolactone and amiloride. Care must be taken when the drug is administered with other potassium-sparing agents, such as angiotensin-converting enzyme inhibitors and angiotensin II receptor-blocking agents. Drug interactions have been reported with lithium, nonsteroidal anti-inflammatory agents, and cardiac glycosides. Triamterene can raise blood glucose levels in patients with adult-onset diabetes mellitus. Concomitant use of the drug with chlorpropamide can increase the risk of hyponatremia. The drug can be used in pregnancy if clearly indicated; it is not recommended during breast feeding. The usual starting dose is 100 mg/b.i.d. after meals. The daily dosage should not exceed 300 mg. Once symptoms of edema are controlled, the dosage can be reduced to administration every other day or to 50 mg/day. When triamterene is used in combination with other kaluretic diuretics, the initial dosage is 25 mg/day, with increases as needed to a maximum dose of 100 mg/day. Dyrenium® is a familiar potassium-sparing diuretic used in the treatment of symptomatic edema of various etiologies. The drug can also be used in combination with other diuretics in the treatment of hypertension. Monitoring of electrolytes is important to ensure its safe use.