Objective: The aim of the study was to assess the prevalence of polypharmacy and inappropriate drug use in elderly internal-medicine patients in one Austrian center and to define the impact of these and other identified predictors on the occurrence of adverse drug events.
Methods: All patients>or=75 years admitted to selected internal wards of a university hospital were included in a monocentric prospective cohort study over a period of three months. The pre-admission medication of the patients was analyzed with respect to appropriateness by a multidisciplinary team consisting of pharmacists and physicians trained in internal medicine. The medication was evaluated for the occurrence of adverse drug events.
Results: A total of 543 patients were analyzed (median age 82 years; 60.2% female). The mean number of drugs taken was 7.5+/-3.8, with women taking significantly more drugs than men (7.8 vs. 6.8, P=0.013). Overall, 58.4% of the patients fulfilled the given criteria for polypharmacy (>6 drugs). The following factors were associated with polypharmacy: female sex, need for nursing care, high number of discharge diagnoses and high Charlson comorbidity score. Unnecessary drugs were found prescribed in 36.3% of all patients, drugs to avoid (Beers criteria) in 30.1%, duplication in 7.6%, wrong dosage in 23.4% and possible drug-drug interactions in 65.8%. Adverse drug events were identified in 17.8% of the patients (97/543), among whom the adverse drug event was the reason for hospital admission in 56.7% of the cases and a drug-drug interaction was involved in 18.7%. Risk factors for adverse drug events were female sex, polymorbidity, renal dysfunction and inappropriate prescribing.
Conclusion: Polypharmacy, inappropriate prescribing and adverse drug events were highly prevalent in a cohort of elderly internal-medicine patients in Austria. To improve drug safety in this high-risk population, appropriate prescribing might be more important than simply reducing the number of prescribed drugs.