NAPLEX Question of the Week: Nephrology

Do you know how many different types of questions the NAPLEX can ask? Hint: Its not just multiple choice. Today's question will focus on the Ordered-Response Question Format.

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Order the following diuretics from the beginning of the nephron to the end based on where they exert their mechanism of action.

A. Furosemide

B. Spironolactone

C. Acetazolamide

D. Chlorthalidone

Answer with Rationale

One of the formats available for question options on the exam are what is called "Ordered-Response" where you have to place the given choices in a particular order depending on the question. This could be "highest to lowest", "smallest to largest", etc. and so careful attention to wording is required to appropriately answer the question. The correct order for this question would be C-A-D-B. Acetazolamide works in the proximal convoluted tubule so would be first. Next would be furosemide which of course works in the thick ascending limb or "loop" of Henle. Third would be chlorthalidone, a thiazide diuretic which exerts its effect in the distal convoluted tubule. Finally, spironolactone, a potassium-sparing diuretic (also an aldosterone antagonist) works at the end of the nephron in the collecting ducts. Hence by the time you get to the end of the nephron, the water loss potential with these agents is limited compared to loop diuretics which decrease reabsorption of significant volume within the loop of Henle. This is why loops are the diuretic class used primarily for heart failure management when patients require volume removal.

For more reading on diuretic mechanism of action, check out this resource on AccessPharmacy:

Christopher M. Bland

Clinical Professor, University of Georgia College of Pharmacy

Dr. Christopher M. Bland is a Clinical Professor at the University of Georgia College of Pharmacy at the Southeast GA campus in Savannah, GA. Dr. Bland has over 20 years of academic and clinical experience in a number of clinical areas. He is a Fellow of both the Infectious Diseases Society of America as well as the American College of Clinical Pharmacy. He is co-founder of the Southeastern Research Group Endeavor, SERGE-45, with over 80 practitioners across 14 states involved. Dr. Bland serves as Associate Editor for the NAPLEX Review Guide 4th edition as well as Editor-In-Chief for the Question of the Week. He has provided live, interactive reviews for more than 10 Colleges/Schools of Pharmacy over the course of his career.