Adverse Drug Reactions in United States Hospitals

C. A. Bond, PharmD, FASHP, FCCP; Cynthia L. Raehl, PharmD, FASHP, FCCP


Pharmacotherapy. 2006;26(5):601-608. 

In This Article

Abstract and Introduction


Adverse drug reactions (ADRs) were examined in 8,208,960 hospitalized Medicare patients in 1998. A database was constructed from the 1998 MedPAR database. The study population was composed of 141,398 Medicare patients who experienced an ADR (rate of 1.73%). The most common drug classes associated with ADRs were cardiotonic glycosides, adrenal corticosteroids, antineoplastic agents, anticoagulants, and analgesics. The most common associated diagnoses were hypertension, congestive heart failure, atrial fibrillation, volume depletion disorders, and atherosclerotic heart disease. In patients who experienced an ADR, death rates were 19.18% higher with 1971 excess deaths (odds ratio 1.208, 95% confidence interval 1.184-1.234), and length of hospital stay was 8.25% higher with 77,769 excess patient-days (Mann-Whitney U test [U]=200078720610, p<0.0001). Charges for patients with an ADR were increased as follows: total Medicare 19.86% ($339,496,598, U=200089611739, p<0.0001), drugs 9.15% ($24,744,650, U=208719928502, p<0.0001), and laboratory charges 2.82% ($6,221,512, U=195143498450, p<0.0001). We developed a list of high-risk diagnoses and drug classes to help pharmacists target patients who are more likely to experience ADRs. This is the first study to evaluate the ADRs in a large population of hospitalized Medicare patients. These findings will enable pharmacists to develop better management programs for ADRs.


Much attention has been focused on the safety of drug therapies in the United States over the last decade. However, few publications have documented the rate and prevalence of adverse drug reactions (ADRs).[1,2] Clearly, improved hospital systems have resulted in fewer medication errors over the last 10 years, but little attention has been directed to the safety of individual drugs and devices.[3] With the recent withdrawal of rofecoxib (Merck & Co., Inc.) and valdecoxib (Pfizer Inc.) due to the increased risk of associated cardiovascular events, health care professionals and the general public have begun to focus on the adverse effects of drugs.[4,5,6,7] Because of concerns regarding rofecoxib, valdecoxib, and alarming adverse effects associated with other drugs, the editors of the Journal of the American Medical Association have recommended that the United States government consider establishing an independent drug safety board to track the safety of drugs and medical devices after they are approved and in widespread use.[8] The U.S. Food and Drug Administration (FDA) recently developed a drug safety panel to monitor drugs for adverse drug reactions.[9]

Much of the drug safety literature over the last 15 years focuses on adverse drug events (ADEs). Adverse drug event is an expansive term that includes all things that can go wrong with drug therapy, such as errors in prescribing, dosing, and formulation; negligence; and ADRs. The need to explore the components of ADEs continues, and ADRs are one of the common subtypes of ADEs. Based on the literature from 1964-1996, overall incidence of ADRs in hospitalized patients was 6.7% (range 1.2-24.1%), and of fatal ADRs 0.32% (0.1-0.85%).[10]

These aggregate figures translate to 2,216,000 hospitalized patients/year who experience a serious ADR and 106,000/year who die from an ADR. Fatal ADRs rank fourth to sixth in leading causes of death.[2] As sobering as these figures appear, ADRs also are one of the more frequent causes of hospitalization (3.7-6.5% of patients).[11,12] Cost estimates for these ADRs are $1.56-$4 billion/year,[13,14] and as many as half of them may be preventable.[10]

To our knowledge, this study is the first to quantify ADRs and evaluate the impact of ADRs in a large number of hospitals and a large patient population. Also, it is the first study to evaluate clinical and economic outcomes of ADRs in a large population of Medicare patients.