Adverse drug events associated with hospital admission.

OBJECTIVE: To increase the knowledge base on the frequency, causality, and avoidability of adverse drug events (ADEs) as a cause for admission in internal medicine or when occurring during hospitalization. METHODS: A prospective study was performed for 6 periods of 8 days each. Epidemiologic data (e.g., age, gender, medical history), drug utilization, and adverse drug reactions on patients hospitalized during these periods were collected by a pharmacy student. RESULTS: A total of 156 patients (70 men and 86 women) were included in the study. The patients' mean age +/- SD was 66.5 +/- 18.1 years and mean length of stay was 13.2 +/- 9 days. Renal and hepatic insufficiency and previous history of drug intolerance were observed in 17.9%, 10.2%, and 2% of the hospitalized patients, respectively. Thirty-eight ADEs occurred in 32 patients; in 15 cases, ADEs were identified as the reason for admission, 10 cases occurred during hospitalization, and 13 cases were present at admission, but were not the cause of admission. The most frequent ADEs involved the neurologic (23.6%), renal (15.7%), and hematologic (13.1%) systems. Among these 38 ADEs, 22 were considered avoidable (57.9%); 20 of these were associated with therapeutic errors (inappropriate administration, drug-drug interactions, dosage error, drug not stopped despite the onset of ADEs). Patients with ADEs stayed longer in the hospital and took more drugs both before and during their hospital stay (p < 0.05). CONCLUSIONS: Most of the ADEs observed in this study were avoidable. The risk/benefit ratio of administered drugs could be improved with better knowledge of the patients' medical history and the risk factors of ADEs.