Triamterene interferes with the process of cationic exchange by blocking luminal sodium channels in the late distal convoluted tubule and collecting duct. Sodium channel
inhibitors block the reabsorption of sodium ion and inhibit the secretion of potassium ion. Aldosterone is not antagonized by triamterene. The net result is increased
sodium and chloride ion excretion in the urine and almost no potassium excretion. Triamterene is more than 70% absorbed on oral administration。
The diuretic effect occurs rapidly (~30 minutes) and reaches a peak plasma concentration in 2 to 4 hours, with a duration of action of more than 24 hours. Triamterene is
extensively metabolized, and some of the metabolites are active as diuretics. Both the drug and its metabolites are excreted in the urine.
Clinical Use
Triamterene is useful in combination with a thiazide or loop diuretic in the treatment of edema or hypertension. Liddle's syndrome also may be treated with a sodium
channel blocking drug, such as triamterene. Triamterene is administered initially in doses of 100 mg twice a day. A maintenance dose for each patient should be
individually determined. This dose may vary from 100 mg a day to as low as 100 mg every other day.
Nebenwirkungen
The most serious side effect associated with the use of triamterene is hyperkalemia. For this reason, potassium supplements are contraindicated, and serum potassium
levels should be checked regularly. Triamterene also is used in combination with hydrochlorothiazide. Here, the hypokalemic effect of the hydrochlorothiazide counters
the hyperkalemic effect of the triamterene. Other side effects that are seen with the use of triamterene are nausea, vomiting, and headache.
