Safety of furosemide administration in an elderly woman recovered from thiazide-induced hyponatremia

BackgroundElderly women are at risk to develop severe hyponatremia after thiazide but not loop diuretic administration. In patients with previous thiazide-induced hyponatremia, the risk for recurrent hyponatremia after furosemide has not been established.MethodsIn order to determine how both diuretics affect water metabolism, we here compare the effects of a rechallenge with either amiloride-hydrochlorothiazide fixed association (AmHTZ; amiloride chlorhydrate 5 mg + hydrochlorothiazide 50 mg; Moduretic™) or furosemide (F; 40 mg; Lasix™) on water excretion in a 79 year old woman who was previously admitted for severe symptomatic hyponatremia secondary to a 5 days course of AmHTZ for systolic hypertension. After correction of initial hydromineral disturbances, a standard oral water load (WL; 20 mL per kg body weight) was administered before, during and after AmHTZ or F challenges.ResultsHyponatremia developed after AmHTZ but not after F challenge. A negative free water clearance (CH2O) was only observed during AmHTZ (− 0.39 mL/min), while maximal CH2O during F was 3.17 mL/min. Based on the results obtained during WL, the calculated maximal daily electrolyte free water clearance ability was only 888 mL after AmHTZ but 10,166 mL after F therapy. Taking into account a measured mean daily water intake of 1830 mL, severe hyponatremia could be predicted to occur after a few days treatment with AmHTZ. In comparison, F appears to be safer, without risk of hyponatremia, during an equivalent period of time.ConclusionsWe here showed that F may be administered to a patient with previous AmHTZ induced hyponatremia without risk for recurrent hyponatremia.