Introduction

Adverse drug events (ADEs) are a significant cause of morbidity and mortality. In the United States, the annual cost of these events has been estimated at nearly $150 billion.^[1] Within the past decade, ADEs have been the focus of many studies in patient safety and quality control, and have been recognized as a top priority in safety efforts due to their iatrogenic nature.^[2-4]

Epidemiologic studies regarding the scope of these adverse events have found:

• About 3% to 28% of all hospital admissions are related to ADEs^[5-9];
• An estimated 5% to 20% of patients experience an ADE during their hospitalizations^[10];
• Elderly patients (> 65 years) are 2.5 times as likely to have an ADE that requires an emergency room visit compared with the general population, and they are 8 times as likely to require hospitalization^[11];
• Drugs with narrow therapeutic indices and/or those that require outpatient therapy monitoring account for 41.5% of all drug-induced hospitalizations^[11]; and
• Nearly two thirds of adverse drug reactions that required hospitalizations were considered to be potentially preventable.^[12]

The potential for preventing ADEs is a key element of efforts to improve patient care.