GENERIC NAME: triamterene and hydrochlorothiazide (HCTZ)
BRAND NAMES: Maxzide, Dyazide
DRUG CLASS AND MECHANISM: Triamterene/hydrochlorothiazide is an oral diuretic (water pill) that is used for treating high blood pressure (hypertension) and edema (water accumulation). It is a combination of two different diuretics. The FDA approved triamterene/hydrochlorothiazide in December 1965.
The kidneys control the amount of sodium and water within the body. Normally, blood circulates through the kidneys where much of the water, sodium and other small molecules are filtered out of the blood and into the tubules of the kidney. Once in the tubules, much of the water and sodium are reabsorbed back into the blood. The water and sodium that is not reabsorbed passes on through the tubules and becomes urine that is eliminated from the body. Diuretics affect the reabsorption of sodium and water from the tubules and thus, the amount of sodium and water retained or eliminated by the body. In addition to controlling sodium, the kidney also controls the amount of potassium that is retained or eliminated from the body.
Diuretics eliminate salt (sodium) and water from the body. Hydrochlorothiazide is a diuretic that can be used alone for treating high blood pressure and edema. It works by blocking sodium and water reabsorption in the kidneys, thereby reducing sodium and water in the body. (Whereas it is clear how hydrochlorothiazide eliminates water from the body, its mechanism of action in lowering high blood pressure is not well understood.) To compensate for the increased amount of sodium and water in the tubules that will be lost as urine, the kidney tries to reabsorb more sodium and water. It does this by removing potassium from the blood and putting it into the tubules in exchange for sodium (and water) in the tubules. As a result, blood potassium levels fall. Triamterene is a diuretic that prevents reabsorption of sodium in exchange for potassium. Thus, it reduces sodium and water in the body but also prevents the depletion of potassium. For this reason, triamterene is called a potassium sparing diuretic. By combining hydrochlorothiazide with triamterene, sodium and water are eliminated from the body without the loss of potassium. However, this drug may allow potassium levels to increase so potassium levels should be closely monitored.
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