care enrollees aged 65 and older. The cost in 2000 per preventable ADE was estimated at $1,983, while national annual costs were estimated at $887 million.

In addition to the likelihood of underestimation, the above estimates are characterized by some important omissions. First, the costs of some highly common medication errors, such as drug use without a medically valid indication and failure to receive drugs that should have been prescribed, were excluded from the Medicare study of ambulatory ADEs (Field et al., 2005). Moreover, the costs of morbidity and mortality arising from the failure of patients to comply with prescribed medication regimens were not assessed. Second, all the studies omitted some important costs: lost earnings, costs of not being able to carry out household duties (lost household production), and compensation for pain and suffering. Third, few data are available for any setting regarding the costs of medication errors that do not result in harm. While no injury is involved, these errors often create extra work, and the costs involved may be substantial.

Effective Error Prevention Strategies Are Available

According to most studies, at least a quarter of all harmful ADEs are preventable. Moreover, many efficacious error prevention strategies are available, especially for hospital care. In the hospital setting, there is good evidence for the effectiveness of computerized order entry with clinical decision-support systems (Bates et al., 1998), for clinical decision-support systems themselves (Evans et al., 1994), and for pharmacist participation on hospital rounds (Leape et al., 1999). Bar coding and smart intravenous (IV) pumps show promise for the hospital setting, but their efficacy has not yet been clearly demonstrated.

Interventions consisting of educational visits appear to hold promise for improving prescribing practices and patient outcomes in nursing homes. Involving pharmacists in the management of medications in nursing homes and ambulatory care also shows promise, but requires additional study. This intervention has been most successful to date in populations with certain conditions, such as diabetes.


Achieving the patient-centered model of care envisioned in the IOM report Crossing the Quality Chasm: A New Health System for the 21st Century (IOM, 2001) will require a paradigm shift away from a paternalistic, provider-centric model of care. Consumers (and their surrogates) should be empowered as partners in their care, with appropriate communication, information, and resources in place to support them. For medication safety,

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