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• Total national costs (lost income, lost household production, disability, health care costs) are estimated to be between $37.6 billion and $50 billion for adverse events and between $17 billion and $29 billion for preventable adverse events.6 Health care costs account for over one-half of the total costs. Even when using the lower estimates, the total national costs associated with adverse events and preventable adverse events represent approximately 4 percent and 2 percent, respectively, of national health expenditures in 1996.7 In 1992, the direct and indirect costs of adverse events were slightly higher than the direct and indirect costs of caring for people with HIV and ADS.8

• In terms of lives lost, patient safety is as important an issue as worker safety. Although more than 6,000 Americans die from workplace injuries every year,9,10 in 1993 medication errors are estimated to have accounted for about 7,000 deaths.11 Medication errors account for one out of 131 outpatient deaths and one out of 854 inpatient deaths.

• Medication-related errors occur frequently in hospitals; not all result in actual harm, but those that do are costly. One recent study conducted at two prestigious teaching hospitals found that almost two percent of admissions experienced a preventable adverse drug event, resulting in average increased hospital costs of $4,700 per admission or about $2.8 million annually for a 700-bed teaching hospital.12 If these findings are generalizable, the increased hospital costs alone of preventable adverse drug events affecting inpatients are about $2 billion for the nation as a whole.

• Hospital patients represent only a fraction of the total population at risk of experiencing a medication-related error. In 1998, nearly 2.5 billion prescriptions were dispensed by U.S. pharmacies at a cost of about $92 billion.13 Numerous studies document errors in prescribing medications,14,15 dispensing by pharmacists,16 and unintentional nonadherence on the part of the patient.17 Medication errors have the potential to increase as a major contributor to avoidable morbidity and mortality as new medications are introduced for a wider range of indications.

This chapter provides a summary of findings in the literature on the frequency and cost of health care errors and the factors that contribute to their occurrence.

Introduction

Although the literature pertaining to errors in health care has grown steadily over the last decade and some notable studies are particularly strong