Considering additive effects of polypharmacy: Analysis of adverse events in geriatric patients in long-term care facilities

BACKGROUND: Potential additive effects of polypharmacy are rarely considered in adverse events of geriatric patients living in long-term care facilities. Our aim, therefore, was to identify adverse events in this setting and to assess plausible concomitant drug causes. METHODS: A cross-sectional observational study was performed in three facilities as follows: (i) adverse event identification: we structurally identified adverse events using nurses’ interviews and chart review. (ii) Analysis of the concomitantly administered drugs per patient was performed in two ways: (ii.a) a review of summary of product characteristics for listed adverse drug reactions to identify possible causing drugs and (ii.b) a causality assessment according to Naranjo algorithm. RESULTS: (i) We found 424 adverse events with a median of 4 per patient (range 1–14) in 103 of the 104 enrolled patients (99%). (ii.a) We identified a median of 3 drugs (range 0–11) with actually occurring adverse events listed as an adverse drug reaction in the summary of product characteristics. (ii.b) Causality was classified in 198 (46.9%) of adverse events as “doubtful,” in 218 (51.2%) as “possible,” in 7 (1.7%) as “probable,” and in 1 (0.2%) adverse event as a “definitive” cause of the administered drugs. In 340 (80.2%) of all identified adverse events several drugs simultaneously reached the highest respective Naranjo score. CONCLUSION: Patients in long-term facilities frequently suffer from many adverse events. Concomitantly administered drugs have to be frequently considered as plausible causes for adverse events. These additive effects of drugs should be more focused in patient care and research.