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.