NAPLEX (North American Pharmacist Licensure Examination) Practice Exam

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What effect do loop diuretics have on electrolyte levels?

  1. Increase K, Mg, Ca, and Na

  2. Decrease K, Mg, Ca, and Na

  3. Increase K and Mg, decrease Ca and Na

  4. Decrease K and Mg, increase Ca and Na

The correct answer is: Decrease K, Mg, Ca, and Na

Loop diuretics, such as furosemide and bumetanide, primarily work by inhibiting the reabsorption of sodium and chloride in the thick ascending loop of Henle in the kidneys. This mechanism leads to increased urine output and subsequent loss of sodium, potassium, calcium, and magnesium in the urine. Therefore, loop diuretics will decrease potassium (K), magnesium (Mg), calcium (Ca), and sodium (Na) levels in the body, making choice B the correct answer. Option A is incorrect because loop diuretics do not increase potassium, magnesium, calcium, and sodium levels in the body. Option C is also incorrect as loop diuretics are not known to increase potassium and magnesium levels while decreasing calcium and sodium levels. Option D is incorrect because loop diuretics do not decrease potassium and magnesium while increasing calcium and sodium levels.