Adverse drug reactions in a department of systemic diseases-oriented internal medicine: prevalence, incidence, direct costs and avoidability

Objective: Adverse drug reactions (ADRs) are a major cause of hospital admi ssion and in-hospital morbidity. Departments of internal medicine are at th e forefront of this problem. To increase the knowledge base, we did a study of the frequency, hazard function, avoidability, and cost of ADRs as a cau se for admission in internal medicine, or when occurring after admission. Methods: This prospective cohort study was based on all admissions to an in ternal medicine unit over a 4-month period. Patients were intensively follo wed in order to assess any ADR occurring during the hospital stay. Causalit y, direct costs, and preventability were assessed. Results: Of 444 admissions (2569 patient-days), 156 ADRs occurred in 116 pa tients (26.1% of all admissions); 95 (21.4%) of these had ADRs at admission , which were the reason for admission in 32 (7.2%). Twenty-one patients (4. 7%) presented with 26 ADRs during hospitalization. The in-hospital ADR inci dence rate was 10.1 per 1000 patient-days. The cost of ADRs leading to hosp italization was estimated at Euro 11,357 per hospital bed per year. Eighty percent of ADRs could be considered preventable. Conclusion: ADRs in hospitalized patients are common and often preventable. Since most ADRs occurred before admission, prevention strategies should pr eferentially target primary health care providers.