Adverse Drug Events

About 2.7 billion prescriptions were filled in the United States in 1998. Although prescription drugs have great clinical benefits, serious adverse drug events can lead to hospitalization, disability, and even death. Adverse drug events are caused by harmful drug reactions or by medication errors committed by health care professionals and patients. Two factors that can increase the risk of a patients' suffering from an adverse drug event are illness severity and intensity of treatment, including taking several drugs simultaneously. Although it is clear that a wide range of commonly used drugs cause adverse drug events with potentially serious consequences for patients, relatively little is known about their frequency. Data routinely collected on adverse drug events during clinical trials or after drugs are marketed are intended to identify the adverse drug events that are associated with particular drugs and do not focus on their frequency. Information on the overall incidence of adverse drug events from all drugs has been limited to a few research studies that typically examined the experience of patients in one of two specific institutions--generally hospitals or sometimes nursing homes--leaving the overall incidence of adverse drug events in outpatient care largely unexplored. Greater understanding of certain factors that affect the likelihood of adverse drug events has led researchers and patient safety advocates to suggest a range of measures to decrease their number and severity. These proposals range from better communication between doctors and patients about the risks and benefits of medications to accelerating research on the safety of marketed drugs. Suggestions for reducing medication errors include developing computerized prescribing and dispensing systems to detect possible errors, increasing the role of pharmacists as advisers to physicians and as monitors of drug therapy, and improving health care providers' pharmaceutical education. This testimony summarizes the January 2000 report, GAO/HEHS-00-21.

GAO noted that: (1) ADEs are the subset of adverse events (injuries) stemming from drug medical treatment; (2) ADEs involve transient and less severe side effects from drugs, such as nausea or rash; (3) many ADEs arise from previously known or newly detected adverse reactions to drugs, and others result from medication errors committed by health care professionals in prescribing or administering drugs or the patients themselves in taking them; (4) sicker patients are more susceptible to suffering negative effects from a single drug; (5) most medication errors do not result in ADEs; (6) nonetheless, an estimated quarter to half of all ADEs among hospital patients result from medication errors; (7) certain classes of drugs have been consistently associated with medication errors; (8) relatively little is known about the incidence and cost of ADEs; (9) data routinely collected on ADEs tend to focus only on the adverse reactions of particular drugs and do not focus on their frequency; (10) information on the incidence of ADEs from all drugs is limited to a few research studies, which typically examine patients in hospitals or nursing homes, leaving the incidence of ADEs in outpatient care largely unexplored; (11) the most broadly based information on ADE incidence comes from two statewide studies of hospital patients that restricted the definition of ADE and found that ADEs occurred at a rate of 0.56 for every 100 patients admitted in Colorado and Utah and 0.72 in New York; (12) other studies of single hospitals that used broader definitions found a range of 2 to 30 ADEs per 100 hospital admissions; (13) two studies in nursing homes reported an incidence of 0.44 to 0.71 ADEs per patient month; and (14) to decrease the number and severity of ADEs caused by both adverse reactions and medication errors, patient safety advocates and researchers have suggested that: (a) improved communication between patients and physicians about the risks and benefits of medications might help to prevent serious drug reaction; (b) expanding and accelerating research on the safety of drugs already on the market could more quickly detect previously unknown adverse reactions and determine the risk factors that increase their likelihood; and (c) developing computerized prescribing and dispensing systems, avoiding sound-alike names and lookalike packaging for medications, increasing the role of pharmacists, and improving health care providers' pharmaceutical education could reduce medication errors.