Determination of the incidence of potentially inappropriate medications and drug interactions: Effect on clinical outcome in elderly patients

Abstract

Introduction: Elderly individuals are a heterogeneous population, with several chronic diseases that require multiple medications, thus increasing the risk of adverse drug events, drug-drug interactions (DDIs) and inappropriate prescribing (IP). Aim of the work: To evaluate the frequency and risk factors for IP and DDIs in hospitalized elderly patients. Methods: Prospective data were collected from 320 elderly patients aged ≥ 65 years, hospitalized in a university teaching hospital over a seventeen month study period. The IP frequency was evaluated using STOPP/START criteria, whilst DDIs were evaluated by Lexi-comp’s Drug Interaction book. Particular socio-demographic and clinical characteristics, as well as comorbid medical conditions were evaluated among possible risk factors for IP and DDIs. Results: The total number of medications prescribed was 2985; median number of medications per patient was nine (range 2-20). According to STOPP/START criteria, 42.8% of the study subjects had at least one potentially inappropriate medication (PIM), whilst 61.9% of the study subjects had at least one potentially prescribing omission (PPO). Out of the 320 studied elderly patients, 239 had DDIs (74.7%). Logistic regression showed that higher number of medications prescribed was an independent risk factor for PIMs and DDIs whereas higher number of morbidities was an independent risk factor for PIMs and PPOs. Conclusion: The present study clearly identified poly-pharmacy as a common major risk factor for PIMs and DDIs whereas poly-morbidity was found to be a common major risk factor vi for PIMs and PPOs. Taken together, the findings of this study indicate that, in order to reduce the possibility of IP and occurrence of DDIs, physicians need to consider these problems when prescribing drugs to elderly patients with multiple chronic diseases who are taking multiple medications. Key words: STOPP/START criteria, elderly, inappropriate prescribing, risk factors.