Background: Adverse drug events (ADEs) remain a key contributor to hospitalisations, resulting in long hospital stays and readmissions. Information pertaining to the specific medications and clinical factors associated with these outcomes is limited. Hence, a better understanding of these factors and their relationship to ADEs is required.

Objectives: To investigate medications involved, clinical manifestations of ADE-related hospitalisations, and their association with length of stay and readmission.

Methods: A retrospective medical record review of patients admitted to a major, tertiary referral hospital in NSW, Australia, from January 2019 to August 2020 was conducted. ADEs were identified using Australian Refined Diagnosis Related Group (AR-DRG) codes: X40, X61, X62 and X64. Medications were classified per the Anatomical Therapeutic Chemical (ATC) classification system and clinical symptoms were classified per the International Classification of Disease (ICD) 9-CM. Logistic regression was performed to assess the relationship between medication and presentation classes with length of stay (≥2 days vs <2 days) and readmission.

Results: There were 125 patients who met inclusion criteria (median age = 64 [interquartile range, 45–75] years; 53.6% male). Anti-thrombotic agents, opioids, antidepressants, antipsychotics, insulins and NSAIDs were the most implicated pharmacological classes. Neurological medications and falls were associated with a length of stay ≥2 days (adjusted odds ratio [aOR] 3.92, 95% confidence interval [CI] 1.48–10.33 and aOR 3.24, 95% CI 1.05–10.06, respectively). Neurological medications and neurological and cognitive disorders were associated with an increased likelihood of 90-day readmission (aOR 2.63, 95% CI 1.05–6.57 and aOR 3.20, 95% CI 1.17–8.75, respectively).

Conclusion: This study identified neurological medications as high-risk for increased length of stay and readmission in those hospitalised due to ADEs. This highlights the need for judicious prescribing and monitoring of these medications.