The Silent Epidemic of Thiazide‐Induced Hyponatremia

Abstract

(Greenwich). 2008;10:477-484 . © 2008 Le Jacq C onsiderable attention is paid to the problem of thiazide-induced hypokalemia. Much less attention is paid to thiazide-induced hyponatremia (tih), which is seen with considerable frequency. tih occurs predominantly in the elderly.1-4 as a result, it is not encountered in the data of large drug treatment trials that involve predominantly younger patients. however, in the systolic hypertension in the Elderly program (shEp), which focused on older patients, hyponatremia (defined as a sodium level <130 mEq/L) was observed in 4.1% of patients treated with chlorthalidone vs 1.3% in the control group, while hypokalemia (potassium level <3.2 mEq/L) was observed in 3.9% of patients in the treatment group.5 thirty percent of patients were receiving 12.5 mg of chlorthalidone, and 60% were receiving 25 mg.5 in another study in the elderly, diuretic-induced hyponatremia, defined as a serum sodium concentration ≤130 mEq/L, was seen in 17% and hypokalemia in 6.6%.6 fiftythree percent of patients were receiving a thiazide diuretic and 24% a loop diuretic. 6 in patients with tih, an average daily hydrochlorothiazide dose of 35 mg has been reported, with 44% of patients having received ≥50 mg.7 however, in 10% of cases the dose was only 12.5 mg.8 the risk of tih is 3-fold higher in persons older than 70 years and is higher among women, possibly because of smaller body size or lower sodium intake.2,3 With the high prevalence of hypertension in the elderly and the routine use of thiazide diuretics to treat it, tih is clearly a prevalent problem.CLINICAL PRESENTATION tih can develop acutely or gradually. it can range from mild to severe and from asymptomatic to symptomatic. the onset is within 2 weeks of starting the diuretic in 50% to 90% of cases, but it can occur within a day or two or even after a single dose.3,7-9 hyponatremia can occur after months or years of taking a thiazide and is likely related to subsequent contributory factors such as reduction of R e v i e w P a p e r

Hyponatremia Independent of Osteoporosis is Associated with Fracture Occurrence

“…Thiazide diuretics are widely used as firstline agents in the treatment of hypertension but are complicated in up to 14% of subjects by hyponatremia (21,22). Among subjects aged 65 years and older resident in a nationally representative sample of U.S. nursing homes, thiazide use was associated with increased fracture risk over 1 year of follow-up (23).…”

A case of Gitelman syndrome with severe hyponatraemia and hypophosphataemia

“…The second patient with a serum sodium concentration of 116 mmol/L presented with mixed features of volume depletion and SIADH. (10,11) The third problem noted in our patient was severe hypophosphataemia. Again, the initial key test is the measurement of urinary phosphorus in any case of hypophosphataemia.…”

“…(10) However, an interesting observation is the impairment of free water excretion by thiazide diuretics, leading to slight volume expansion as a primary event. This, in turn, triggers or aggravates hyponatraemia.…”

SIADH following laparoscopic (totally extraperitoneal) inguinal hernia repair

“…In subjects with a moderate impairment of free water excretion, a thiazide will cause hyponatraemia if fluid intake is excessive. 9 There is suggestion that the patient in our case is suspected to have drunk 2-3l of water between his return from theatre and his seizures due to his determination to pass urine and be able to be discharged as soon as possible.…”