Prescribing Safety Assessment (PSA) Practice Exam

Which type of diuretics are known to cause both hypokalaemia and hypernatraemia?

1. Thiazide diuretics

2. Potassium-sparing diuretics

3. Loop diuretics

4. Carbonic anhydrase inhibitors

The correct answer is: Loop diuretics

Loop diuretics are indeed associated with causing both hypokalaemia and hypernatraemia. These diuretics, such as furosemide and bumetanide, act on the thick ascending limb of the loop of Henle, where they inhibit the sodium-potassium-chloride co-transporter. This inhibition leads to increased excretion of sodium, calcium, magnesium, and potassium. The significant loss of potassium through urine results in hypokalaemia, while the loss of sodium can lead to fluid and electrolyte imbalances that may subsequently contribute to hypernatraemia, particularly if there is also excessive fluid loss or inadequate intake. This dual effect is crucial to understand in clinical practice, as it can impact patient management, especially for those on loop diuretics who may require monitoring and potential supplementation of potassium or careful management of sodium levels. Thiazide diuretics, while they can also lead to hypokalaemia, typically do not cause hypernatraemia to the same extent as loop diuretics. Potassium-sparing diuretics tend to retain potassium, thus preventing hypokalaemia. Carbonic anhydrase inhibitors primarily impact bicarbonate reabsorption and may not induce these particular electrolyte imbalances.