Cost evaluation of adverse drug reactions in hospitalized patients in Taiwan: A prospective, descriptive, observational study

Abstract

Background: Adverse drug reactions (AADRs) are a leading cause of morbidity and mortality. In the United States, ADR-related morbidity and mortality costs have been estimated at US $330 billion to US $1130 billion annually.

Objectives: The aim of this study was to evaluate the incidence of ADRs in Taiwan, to identify the drug classes that are most commonly related to ADRs, and to determine the direct medical costs to hospitals associated with prolonged hospitalizations due to ADRs.

Methods: In this prospective, descriptive, observational study, patients who experienced ADRs during their hospitalization at a Taiwan teaching hospital or who were admitted due to an ADR from January 1, 2002, through December 31, 2004, were included in the study. The patients were identified actively by clinical pharmacists and passively by physicians and nurses who reported ADRs. The World Health Organization (WWHO) definition of ADR severity was adopted, and degrees of probability for each ADR were determined using the Naranjo algorithm. The direct medical costs incurred to the hospital in the treatment of ADRs that prolonged hospitalization were calculated (ie, costs of emergency department [ED] visits, intensive care unit visits, extra days of hospitalization, monitoring and laboratory studies, pharmacist dispensing fees, physician fees, room charges, ED charges).

Results: During the study period, 43 of the 142,295 hospitalized patients (00.03%)) were admitted because of an ADR. A total of 564 (00.40%)) of the hospitalized patients were verified to have ADRs. Three hundred eighteen of the patients (56.44%) with ADRs were male and the overall mean (SD) age was 66(2) years. The most common drug classes associated with the ADRs were antibiotics (219 patients [38.8% ]), analgesics (62 [11.0%]), and cardiovascular agents (56 [9.9%]). The systems most commonly involved in ADRs were cutaneous (296 patients [52.5%]), hematologic (61 [10.8%]), and cardiovascular (54 [9.66%]). The causes of the ADRs were anaphylactic (464 patients [82.3%]), drug overdose (78 [13.8%]), and drug-drug interactions (22 [3.9%]). Of the ADRs, 474 (884.0%) were idiosyncratic type B reactions (predictable). ADR-related costs, estimated at US $3489/ADR, were mostly due to prolonged length of stay. Based on the WHO definition, of the 564 ADRs, 330 (58.5%) and 40 (7.1%) were classified as moderate and severe, respectively. Two patients died of ADRs associated with allopurinol.

Conclusion: In this hospital, 0.40% of patients were identified as having ADRs that were associated with high direct costs, mostly due to extended hospitalizations.

Keywords: adverse drug reactions; direct medical cost.