Triamterene is a potassium-sparing diuretic used in the treatment of edema and in the management of hypertension. It can be found under the brand names Dyrenium and Maxzide. Triamterene (2,4,7-triamino-6-phenylpteridine) is a potassium-sparing diuretic that is used in the management of hypertension. It works by promoting the excretion of sodium ions and water while decreasing the potassium excretion in the distal part of the nephron in the kidneys by working on the lumenal side. Since it acts on the distal nephron where only a small fraction of sodium ion reabsorption occurs, triamterene is reported to have limited diuretic efficacy. Due to its effects on increased serum potassium levels, triamterene is associated with a risk of producing hyperkalemia. Triamterene inhibits the epithelial sodium channels (ENaC) located on the lumenal side in the late distal convoluted tubule and collecting tubule, which are transmembrane channels that normally promote sodium uptake and potassium secretion. In the late distal tubule to the collecting duct, sodium ions are actively reabsorbed via ENaC on the luminal membrane and are extruded out of the cell into the peritubular medium by a sodium-potassium exchange pump, the Na-K-ATPase, with water following passively. Triamterene exerts a diuretic effect on the distal renal tubule to inhibit the reabsorption of sodium ions in exchange for potassium and hydrogen ions and its natriuretic activity is limited by the amount of sodium reaching its site of action. Its action is antagonistic to that of adrenal mineralocorticoids, such as aldosterone, but it is not an inhibitor or antagonist of aldosterone. Triamterene maintains or increases sodium excretion, thereby increasing the excretion of water, and reducing the excess loss of potassium, hydrogen, and chloride ions by inhibiting the distal tubular exchange mechanism. Due to its diuretic effect, triamterene rapidly and reversibly reduces the lumen-negative transepithelial potential difference by almost completely abolishing Na+ conductance without altering K+ conductance. This reduces the driving force for potassium movement into the tubular lumen and thus decreases potassium excretion. Triamterene is similar in action to amiloride but, unlike amiloride, increases the urinary excretion of magnesium. Some side effects of using triamterene may include stomach pain, agitation, and cloudy urine.

Triamterene Pathway (New) References