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Hanlon JT, Sloane RJ, Pieper CF, Schmader KE. Adverse drug reactions (ADRs) are associated with both drug-drug and drug-disease interactions in frail elderly outpatients. Poster session presented at: American Geriatrics Society Annual Meeting; 2010 May 16; Orlando, FL.
Purpose: To determine which suboptimal prescribing factors are associated with the adverse drug reactions among frail older veterans transitioning from the hospital to the community. Methods: This cohort study included 359 veterans enrolled in the Geriatric Evaluation and Management Drug Study. Clinical pharmacist-physician pairs reviewed a medical record abstract and medication list and independently rated prescribing appropriateness with the Medication Approriateness Index (MAI) at hospital discharge and potential adverse drug reactions (ADR) with Naranjo's causality algorithm over the following 12 month period. Discordances in MAI and ADR evaluations were resolved during clinical consensus conferences. Multivariable logistic regression was employed to identify factors associated with incidence of an ADR during followup. Results: At least one ADR occurred in 31.8% of outpatients. The frequency order of the four problems detected by the abbreviated MAI in patients was incorrect directions (44.3%), incorrect dosages (41.2%), drug-disease interactions (13.4%) and drug-drug interactions (5.9%). Controlling for demographic and health status factors, both drug-disease interactions (AOR 1.9, 95% CI 1.0-3.6) and drug-drug interactions (AOR 2.4, 95% CI 1.0-6.0) separately or combined (AOR 1.8, 95%CI 1.1-3.3) were associated with an increased risk of ADRs. As expected, since dosage and directions problems could lead to increased or decreased drug concentrations, neither was associated with ADRs (dosage AOR 0.8; 95% CI 0.5-1.2; directions AOR 0.7; 95% CI 0.5-1.2). Conclusions: ADRs are common in elderly veteran outpatients and are particularly associated with drug interactions. Quality improvement activities to reduce ADRs should include a focus on improving medication inappropriateness due to drug interactions.