Background: Previous studies have investigated the prevalence of drug-drug interactions (DDIs) among the elderly in different care settings, but data describing the frequency and management of DDIs among acute geriatric patients appear to be absent.
Objective: The aim of this study was to investigate the severity and interdisciplinary management of DDIs in patients admitted to an acute geriatric ward.
Methods: The study was conducted at Oslo University Hospital, Norway, over a period of 19 weeks in 2010/11. On admission and daily during the hospital stay, prescribed medications were reviewed by pharmacists to identify DDIs with the aid of web-based databases. DDIs defined to be of potential clinical relevance, i.e., those classified as "major" (generally avoid) or "moderate" (precautions recommended), were following assessments by pharmacists presented at interdisciplinary meetings with geriatricians and nurses, and discussed in relation to the possible implementation of monitoring actions or changes in prescribing. The odds for prescribing changes were compared in relation to DDI type ("pharmacokinetic" vs. "pharmacodynamic") and severity ("major" vs. "moderate"). The project group retrospectively assessed the possible causal relationships between hospitalizations and DDIs.
Results: The pharmacists identified 245 DDIs of major (n = 13) or moderate (n = 232) severity in 80 (63.5 %) of the 126 patients included on admission and/or during hospitalization. In 94 of 162 cases where the pharmacists alerted the geriatricians (58.0 %), prescribing changes or monitoring actions were implemented. Prescribing changes (n = 38) were performed significantly more often for major than for moderate DDIs [odds ratio (OR) 3.8; 95 % confidence interval (CI) 1.2-12.2, p = 0.03], and significantly more often for pharmacokinetic than for pharmacodynamic DDIs (OR 4.9; 95 % CI 2.2-10.9, p < 0.01). For 28 of 126 patients (22.2 %), a causal relationship between hospitalizations and DDIs was assessed as "possible".
Conclusions: The present study shows that acute geriatric patients are frequently exposed to DDIs for which active management is recommended in order to avoid unfavorable clinical outcomes. The integration of pharmacists into interdisciplinary teams could prevent potentially severe DDIs in the elderly.