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 admission and in-hospital morbidity. Departments of internal medicine are at the 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 cause for admission in internal medicine, or when occurring after admission.

METHODS

This prospective cohort study was based on all admissions to an internal medicine unit over a 4-month period. Patients were intensively followed in order to assess any ADR occurring during the hospital stay. Causality, direct costs, and preventability were assessed.

RESULTS

Of 444 admissions (2569 patient-days), 156 ADRs occurred in 116 patients (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 incidence rate was 10.1 per 1000 patient-days. The cost of ADRs leading to hospitalization 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 preferentially target primary health care providers.