Drug-related hospitalizations in a tertiary care internal medicine service of a Canadian hospital: a prospective study

STUDY OBJECTIVES: To determine the frequency, severity, preventability, and classification of adverse drug events resulting in hospitalization, and to identify any patient, prescriber, drug, and system factors associated with these events. DESIGN: Prospective, observational study. SETTING: Internal medicine service of a large tertiary care hospital in Canada. PATIENTS: A total of 565 consecutive adult patients admitted to the hospital during a 12-week period. MEASUREMENTS AND MAIN RESULTS: A patient's hospitalization was defined as drug related if it was directly related to one of eight predefined classifications; severity and preventability of the hospitalization were also assessed. Multivariate logistic regression analysis was used to evaluate patient, prescriber, drug, and system factors associated with drug-related hospitalizations. The frequency of drug-related hospitalization was 24.1% (95% confidence interval [CI] 20.6-27.8%), of which 72.1% (95% CI 63.7-79.4%) were deemed preventable. Severity was classified as mild, moderate, severe, and fatal in 8.1% (95% CI 4.1-14.0%), 83.8% (95% CI 76.5-89.6%), 7.4% (95% CI 3.6-13.1%), and 0.7% (95% CI 0.0-4.0%), respectively, of the hospitalizations. The most common classifications of drug-related hospitalization were adverse drug reactions (35.3% [95% CI 27.3-43.9%]), improper drug selection (17.6% [95% CI 11.6-25.1%]), and noncompliance (16.2% [95% CI 10.4-23.5%]). No independent risk factors for drug-related hospitalization were identified with regression modeling. CONCLUSION: Approximately 25% of patients in our study were hospitalized for drug-related causes; over 70% of these causes were deemed preventable. Drug-related hospitalization is a significant problem that merits further research and intervention.