Characterization of Usage Patterns of Drugs Suspected to Cause Adverse Drug Reactions in Older Hospitalized Patients

AIM: This study aimed to characterize the usage patterns of drugs suspected to cause adverse drug reactions (ADRs) in older hospitalized patients. METHODS: Medical records of older adults admitted to the Department of Geriatrics and Hypertension at Osaka University Hospital from September 2014 to August 2021 were reviewed. The probability of ADRs was retrospectively assessed using the Naranjo ADR Probability Scale. Patients were categorized into two groups according to whether the suspected drugs were prescribed before admission (continuous-use group) or were newly initiated or modified after admission (new/changed-use group). The types and frequency of ADRs, timing of ADR onset, and suspected drugs identified were summarized according to the usage patterns. RESULTS: ADRs were identified in 5.6% (n = 79) of eligible hospitalizations (N = 1418). In the continuous-use group (n = 39), antihypertensives were the most frequently identified suspected drugs (46.2%), followed by diuretics (17.9%), analgesics (12.8%), and antidiabetic drugs (7.7%); the most common ADRs were hypotension (35.9%), bradycardia/tachycardia (17.9%), and electrolyte abnormalities (17.9%). In the new/changed-use group, antihypertensives were also the most frequently identified suspected drugs (15.0%), followed by antibiotics, diuretics, antidementia drugs, and analgesics (10.0%); the ADRs included hypotension (22.5%), nausea and vomiting (17.5%), and electrolyte abnormalities (15.0%). Most ADRs occurred within the first week of hospitalization, except for electrolyte abnormalities, which often appeared during the first 2 weeks of hospitalization. CONCLUSIONS: This study identified ADRs and suspected drugs according to the usage patterns in older hospitalized patients. Close monitoring of both newly prescribed and continuously used drugs is crucial, particularly during the first weeks of hospitalization.