Evaluation of potentially inappropriate medication use according to the Asian criteria and its impact on hospitalisation outcomes among older outpatients

Potentially inappropriate medications (PIMs) are associated with adverse outcomes in older adults. The Asian explicit criteria, compiled from 15 quality-assessed country-specific guidelines, provide a regionally relevant and comprehensive framework for evaluating PIM use. This study investigates the prevalence, predictors, and hospitalisation outcomes of PIM use, as defined by the Asian criteria, among older outpatients in Thailand. A retrospective cohort study was conducted using data on patients aged ≥60 years who received outpatient care, obtained from the electronic medical records of three public hospitals in Thailand. Outpatient prescriptions from 2023 were analysed to identify PIM use, categorised into disease-independent, disease-specific, and drug–drug interaction (DDI)-based groups. Predictors were examined using multivariable logistic regression, while associations with hospitalisation outcomes in 2024 were assessed using generalised linear models. Among 76,361 older outpatients (mean age: 69.59 ± 7.63 years; 55.66% female), 82.99% received at least one PIM. The prevalence of disease-independent, disease-specific, and DDI-based PIMs was 82.71%, 31.09%, and 10.24%, respectively. Predictors of PIM use included care at lower-level hospitals, female sex, multimorbidity, and polypharmacy, including hyperpolypharmacy. In adjusted analyses, overall PIM use was significantly associated with a 1.17-fold increased risk of all-cause hospitalisation, 1.86-fold for adverse drug event-related hospitalisation, 1.46-fold for in-hospital mortality, and a higher number of admissions. PIM use was widespread among older outpatients and associated with adverse hospitalisation outcomes. The Asian criteria facilitated a comprehensive and context-specific evaluation of PIMs in Asian settings. Integrating these criteria into clinical practice may enhance prescribing safety and help reduce PIM-related risks.