A Retrospective Case-Control Study Evaluating Thiazide-Induced Hyponatraemia-Related Hospitalisation Among Older Singaporeans

Introduction: Thiazide diuretics are recommended as first-line therapy for hypertension in older adults. However, thiazides are also associated with hyponatraemia-related hospitalisations in older patients. This study aims to determine the predictors of hospitalisation due to thiazides usage in older adults.Methods: This is a retrospective matched case-control study. Patients aged >= 65 admitted due to adverse drug reactions based on International Classification of Diseases, Ninth Revision (ICD9) codes from the period of 1 June to 31 December 2011 in Singapore General Hospital were extracted. Patients with the ICD9 code E944.3 Saluretics causing adverse effects in therapeutic use and who experienced thiazide-induced hyponatraemia were identified. Controls were identified from a pool of patients from outpatient clinics who were prescribed thiazide during the study period. Each case was matched to four controls based on gender and race. Patients' demographics, length of stay, and cost of hospital admission were obtained.Results: In total, 19 cases with thiazide-induced hyponatraemia were matched with 76 controls. Cases were older than control (78.8 +/- 6.1 vs. 75.6 +/- 7.0, p=0.052), with the majority being females (84.2%) and Chinese (94.7%). The mean length of stay was 4 (+/- 3) days; the mean cost of stay was SGD 1118 (+/- 898). Serum potassium levels and concurrent use of betablockers were identified as unadjusted possible predictors for hospitalisation due to thiazide-induced hyponatraemia.Conclusion: Potential predictors of hospitalisation due to thiazide-induced hyponatraemia include low potassium levels and concurrent use of beta-blockers. Identification of predictors is crucial to guide safe and effective prescribing of thiazides in older patients.