A 56-year-old woman arrives at the clinic for a check-up on her heart failure with reduced ejection fraction. The patient has been hospitalized twice in the last three months due to acute decompensation of heart failure that required intravenous furosemide treatment. She has been taking high doses of oral furosemide since her most recent discharge, but she still has progressive lower extremity edema and weight gain. Serum creatinine levels are 1.2 mg/dL and serum potassium levels are 4.1 mEq/L. Metolazone is being administered to the patient. Because of which of the following effects of furosemide is the addition of metolazone likely to aid in the treatment of this patient?

Question

Quizplus · Accepted Answer

Eductional Objective: The main determinant of volume status is sodium. Loop diuretics work by inhibiting the Na-K-2Cl cotransporter in the ascending limb of the loop of Henle, preventing sodium absorption and encouraging sodium and water excretion in the urine. The reabsorption of sodium in the distal convoluted tubule limits the sodium excretion caused by loop diuretics; the Na-Cl cotransporter in the distal tubule counteracts some of the effect of loop diuretics by absorbing much of the sodium that is not absorbed in the loop of Henle. Metolazone inhibits the Na-Cl cotransporter, preventing reabsorption of the increased sodium delivered to the distal tubule and significantly increasing total sodium excretion.

A 56-Year-Old Woman Arrives at the Clinic for a Check-Up