Thiazide-Induced Hyponatremia Presenting as a Fall in an Older Adult

Regardless of age, first-line therapy for uncomplicated hypertension includes thiazide diuretics, long-acting calcium channel blockers, and renin-angiotensin system inhibitors. Even though older adults are often at increased risk of adverse drug events, specific guidelines for choosing between different classes of antihypertensives are lacking. Given the prevalence of hypertension in older adults, clinicians should be aware of the increased risk of electrolyte disorders after the initiation of thiazide diuretics in this population.

A patient aged > 90 years fell getting out of his bed 2 weeks following initiation of hydrochlorothiazide 25 mg daily medication therapy. Laboratory tests revealed a urine sodium of 35 mmol/L most consistent with hypovolemic hypoosmotic hyponatremia secondary to thiazide initiation. Hydrochlorothiazide was discontinued and sodium gradually normalized over the next 2 weeks without any other intervention.

Despite being recommended as first-line therapy for uncomplicated hypertension, thiazide diuretics may cause more harm than good in older adults with risk factors for thiazide-induced hyponatremia, which should be considered before initiation.