Diuretics and hyponatremia

 Q: Which of the diuretic is more prone to cause hyponatremia? (select one)

A) Thiazide

B) Loop

Answer: A

In thiazide diuretics, there is a direct effect of reduced sodium chloride reabsorption without water in the distal tubule, leading to hyponatremia.

Loop diuretics rarely cause hyponatremia. If hyponatremia occurs with loop diuretics, it pinpoints toward other underlying diseases such as congestive heart failure (CHF) or cirrhosis which are by default hyponatremic conditions. This protection of hyponatremia in loop diuretics is because the inhibition of sodium chloride transport in the loop of Henle impairs the generation of the countercurrent gradient. This limits the ability of Anti Diuretic Hormone (ADH) to promote water retention. 

#electrolytes

#nephrology

#pharmacology

References:

1. Szatalowicz VL, Miller PD, Lacher JW, et al. Comparative effect of diuretics on renal water excretion in hyponatraemic oedematous disorders. Clin Sci (Lond) 1982; 62:235. 

2. Filippone EJ, Ruzieh M, Foy A. Thiazide-Associated Hyponatremia: Clinical Manifestations and Pathophysiology. Am J Kidney Dis 2020; 75:256.