is likely that per day, nursing home patients are more likely to experience a medication error than are hospital patients. Monitoring errors are probably the most common type of error in the nursing home setting, but are much more difficult to identify, and no study in this area was found. Because a typical medication pass in long-term care exceeds 2 hours, it is impossible for the nurse to deliver all medications within 1 hour of the scheduled time; thus wrong-time errors are predictably high in this setting. Finally, transitions from the nursing home to other settings are a time of high risk for adverse effects due to prescribing or transcription errors.

Ambulatory Care

For the purposes of this study, the committee examined medication error rates in six different settings within the ambulatory care domain: (1) the interface between care settings, for example, from hospital care to outpatient clinic; (2) the ambulatory clinic; (3) the community pharmacy; (4) the home care setting; (5) self-care; and (6) the school setting. In general, there is little or no understanding of incidence rates in all these areas.

Error rates in ambulatory clinics have been thinly researched (see Table 3-3). One study found that 21 percent of prescriptions in these settings

TABLE 3-3 Error Rates in Ambulatory Clinics

Prescription writing errors

Percentage of prescriptions containing at least one prescription writing error

21 (Shaughnessy and Nickel, 1989)

Errors in an ambulatory hemodialysis unit

Percentage of patients subject to prescribing errors

97.7 (Manley et al., 2003b)


Medication-related problems per patient per month

0.45 (Manley et al., 2003a)

Errors in an ambulatory chemotherapy unit

Percentage of doses containing an error

3 (Gandhi et al., 2005)

Errors in dispensing samples

Percentage of labels with usual dosage not present

12 (Dill and Generali, 2000)


Percentage of labels that referred user to enclosed prescribing information that was absent

17 (Dill and Generali, 2000)

Documentation errors

Current medications per patient missing from patient record

0.37 (Wagner and Hogan, 1996)

0.89 (Bedell et al., 2000)


Percentage of prescription renewals missing from patient record

15 (Ernst et al., 2001)

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