FREQUENCY AND COST OF SERIOUS ADVERSE DRUG-REACTIONS IN A DEPARTMENT OF GENERAL MEDICINE

Aims To assess the frequency and cost of drug reactions causing or pro longing hospitalization. Methods All patients admitted to an internal medicine ward over 6 months were evaluated to identify serious adverse reactions. The number of drug classes on admission or at the time of the adverse drug reaction (ADR) was counted. Excess ADR-related hospit al stay was computed using a) raw excess duration of hospital stay, b) correction of duration of hospital stay by age, sex, and number of dr ug classes, and c) estimation by investigator of excess hospital stay. Results Three hundred and twenty-nine patients were evaluated: 212 ma le, 117 female, mean age 57.2 (males: 52.2, females: 66.2 (P<0.05)), r ange 17-95 years. They stayed a total of 3720 hospital days (mean stay 11.3 days). 298 had no ADR (mean age 55.8, taking a mean of 2.7 drug classes, 10.7 days hospital stay); 31 had ADRs: in 10, the ADR caused admission in patients with a mean age of 84 (P<0.01 vs the two other g roups), taking 6.3 drug classes, who stayed a mean of 15.1 days; 21 oc curred in hospital in patients with a mean age of 63.6, taking 4.2 dru g classes (P<0.01), who stayed a mean of 19.2 days (P<0.01 vs patients without ADRs). In four the ADR was fatal (13% of ADRs, 40% of deaths) . Raw ADR-related excess hospital stay was 318 days (8.6% of all hospi tal days), after multivariate correction 282 days (7.6% of all hospita l days), and with investigator estimation 197 days (5.3% of all hospit al days). Point prevalence of ADRs at admission was 3%, incidence rate in hospital was 5.6/1000 patient-days. Conclusions 3% of the admissio ns were related to ADRs. In addition, 6.6% of hospitalized patients ha d significant ADRs. Between 5 and 9% of hospital costs were related to ADRs. In 24 of the 31 patients with ADRs (77%), these were related to the pharmacological properties of the involved drugs, and may possibl y have been avoidable.