Admissions caused by adverse drug events to internal medicine and emergency departments in hospitals: a longitudinal population-based study.

OBJECTIVE

To estimate incidence rates of drug-related hospitalizations (DRHs) in a longitudinal population-based study with prospective event assessment.

DESIGN

Cohort study and time-trend analysis.

SETTING

All departments of internal medicine and emergency departments in the urban regions of Jena and Rostock, Germany, serving about 520,000 residents.

PARTICIPANTS

All patients admitted between October 1997 and March 2000. Patients with severe cutaneous reactions were excluded.

MAIN OUTCOME MEASURES

Incidence of DRH was defined by symptoms or diagnoses at admission that were very likely, likely, or possibly caused by prescription medications, according to a standardized assessment.

RESULTS

The incidence of DRH was 9.4 admissions per 10,000 treated patients [95% confidence interval (CI) 9.0-9.9]. Rates were highest for antithrombotics with 26.9 admissions per 10,000 treated patients (95% CI 23.6, 30.1). Most frequent events were gastroduodenal lesions and bleeding (45%). Digitalis preparations showed a linearly increasing trend from 2/10,000 to 14/10,000 during ten quarters ( P<0.0001), which was exclusively attributable to digitoxin, the major source of digitalis in the study area (93%). The incidence of DRH increased with age (4/10,000 to 20/10,000). The mean length of stays in patients with DRH was 13+/-10.6 days. Cumulative direct costs for hospitalization were Euro 4 million in the two urban study areas. The annual direct costs for Germany were estimated to be Euro 400 million.

CONCLUSIONS

DRHs are a considerable public health and economic burden. A longitudinal design can observe changes in population-based incidence over time. This approach can be used for public-health planning or to evaluate outcomes of quality management programs designed to reduce drug-induced illness.