International Journal for Quality in Health Care 2005; Volume 17, Number 1: pp. 15–22 10.1093/intqhc/mzi015
International Journal for Quality in Health Care vol. 17 no. 1 © International Society for Quality in Health Care and Oxford University Press 2005; all rights reserved 15

Errors in the medication process: frequency, type, and potential


1Aarhus University Hospital, Department of Quality improvement and Patient Safety, Aarhus, Aarhus, 2Aarhus University Hospital, Department of Clinical Pharmacology, Aarhus, 3National Indicator Project, County of Aarhus, Aarhus, Denmark


Objective. To investigate the frequency, type, and consequences of medication errors in more stages of the medication process, including discharge summaries.

Design. A cross-sectional study using three methods to detect errors in the medication process: direct observations, unan- nounced control visits, and chart reviews. With the exception of errors in discharge summaries all potential medication error consequences were evaluated by physicians and pharmacists.

Setting. A randomly selected medical and surgical department at Aarhus University Hospital, Denmark.

Study participants. Eligible in-hospital patients aged 18 or over (n = 64), physicians prescribing drugs and nurses dispensing and administering drugs.

Main outcome measures. Frequency, type, and potential clinical consequences of all detected errors compared with the total number of opportunities for error.

Results. We detected a total of 1065 errors in 2467 opportunities for errors (43%). In worst case scenario 20–30% of all evalu- ated medication errors were assessed as potential adverse drug events. In each stage the frequency of medication errors were— ordering: 167/433 (39%), transcription: 310/558 (56%), dispensing: 22/538 (4%), administration: 166/412 (41%), and finally discharge summaries: 401/526 (76%). The most common types of error throughout the medication process were: lack of drug form, unordered drug, omission of drug/dose, and lack of identity control.

Conclusion. There is a need for quality improvement, as almost 50% of all errors in doses and prescriptions in the medication process were caused by missing actions. We assume that the number of errors could be reduced by simple changes of existing procedures or by implementing automated technologies in the medication process.

Keywords: Medication errors, potential adverse drug events, chart review, direct observation, unannounced control visit

Medication errors are a well-known problem in hospitals. Studies have shown that medication errors and adverse drug reactions (ADRs) are one of the main causes for adverse events in hospitals leading to disability and death in up to 6.5% of hospital admissions [1–5].

Not all medication errors are harmful. Previous studies of the association have shown that <1% of all medication errors actually resulted in an adverse drug event, while up to 6.7% were assessed as potential adverse drug events, when exam- ined primarily by chart reviews [3,6,7]. However, a study using direct observation to detect medication errors in the dispens- ing and administration stage assessed 20% of the identified errors as potential adverse drug events [8]. Thus, application of appropriate methods for identifying medication errors and

assessing potential adverse drug events are important in the detection of valid and useful information [9,10].

The literature on medication errors lacks universally accepted definitions of medication errors as well as different methods and criteria, leaving us with an incomplete know- ledge of the actual rate of medication errors [1–5,7,8,11–14]. Likewise, criteria for assessing the potential clinical conse- quences of medication errors vary in different studies [3,8,15]. At present, no studies have investigated medication errors in more stages of the process in the same population including discharge summaries. In addition, no studies have investi- gated medication errors in more stages of the medication process by selecting the most appropriate and valid methods at each stage.