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Chapter 15: Diuretics & Other Drugs That Act on the Kidney

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A 70-year-old retired businessman is admitted with a history of recurrent heart failure and metabolic derangements. He has marked peripheral edema and metabolic alkalosis. Which of the following drugs is most appropriate for the treatment of his edema?

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(A) Acetazolamide

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(B) Digoxin

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(C) Dobutamine

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(D) Eplerenone

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(E) Hydrochlorothiazide

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Although acetazolamide is rarely used in heart failure, carbonic anhydrase inhibitors are quite valuable in patients with edema and metabolic alkalosis. The high bicarbonate levels in these patients make them particularly susceptible to the action of carbonic anhydrase inhibitors. Digoxin is useful in chronic systolic failure but is not first-line therapy. Dobutamine is appropriate only when diuresis has already been accomplished in severe acute failure. Hydrochlorothiazide and spironolactone are not adequate for first-line therapy of edema in failure. The answer is A.

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A 50-year-old man has a history of frequent episodes of renal colic with calcium-containing renal stones. A careful workup indicates that he has a defect in proximal tubular calcium reabsorption, which results in high concentrations of calcium salts in the tubular urine. The most useful diuretic agent in the treatment of recurrent calcium stones is

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(A) Chlorthalidone

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(B) Diazoxide

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(C) Ethacrynic acid

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(D) Mannitol

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(E) Spironolactone

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The thiazides are useful in the prevention of calcium stones because these drugs reduce tubular calcium concentration, probably by increasing passive proximal tubular and distal convoluted tubule reabsorption of calcium. In contrast, the loop agents (choice C) facilitate calcium excretion. Diazoxide is a thiazide-like vasodilator molecule but has no diuretic action; in fact, it may cause sodium retention. It is used in hypertension and insulinoma (see Chapter 11). The answer is A.

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Which of the following is an important effect of chronic therapy with loop diuretics?

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(A) Decreased urinary excretion of calcium

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(B) Elevation of blood pressure

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(C) Elevation of pulmonary vascular pressure

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(D) Metabolic alkalosis

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(E) Teratogenic action in pregnancy

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Loop diuretics increase urinary calcium excretion and decrease blood pressure (in hypertension) and pulmonary vascular pressure (in congestive heart failure). They have no recognized teratogenic action. They cause metabolic alkalosis (Table 15–1...

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