Hospital admissions due to drug-related hyponatraemia

Little is known about morbidity due to drug-related hyponatraemia, despite hyponatraemia being a common side effect of frequently prescribed medicines. We conducted a 12-month retrospective service evaluation of hospital admissions due to drug-related hyponatraemia to determine what drugs are contributing factors, describe patient demographics and burden of morbidity. This was undertaken at a large acute UK hospital and drug-related hyponatraemia was defined by admissions where hyponatraemia was coded as the principal diagnosis and specific medication(s) were recorded as either contributory factor(s) or the principal cause of hyponatraemia and these medication(s) were discontinued. Of 131 hyponatraemia admissions, 71 (54%) were drug-related. Angiotensin converting enzyme inhibitors/ angiotensin receptor blockers, proton pump inhibitors and thiazide diuretics were drug classes most commonly associated. 61% of patients were women, median age 81 (IQR15.5) years, 61% were on more than 2 implicated drugs. The median length of stay was 4 (2-9 days IQR). This study highlights that elderly woman on more than 2 drugs that can cause hyponatraemia, constituted the majority of patients admitted to hospital with drug-related hyponatraemia.