To identify and analyse factors underlying intern prescribing errors to inform development of specific medication-safety interventions.

A prospective qualitative study that involved face-to-face interviews and human-factor analysis.

A tertiary referral teaching hospital, Brisbane, Queensland, February–June, 2004.

Fourteen intern prescribers involved in 21 errors.

A structured questionnaire was used to identify factors causing the errors. Transcripts were analysed on the basis of human-error theory to identify underlying themes.

Factors underlying prescribing errors.

Errors were multifactorial, with a median of 4 (range, 2–5) different types of performance-influencing factors per error. Lack of drug knowledge was not the single causative factor in any incident. The factors in new-prescribing errors included team, individual, patient and task factors. Factors associated with errors in represcribing were environment, task and number of weeks into the term. Defences against error, such as other clinicians and guidelines, were porous, and supervision was inadequate or not tailored to the patient, task, intern or environment. Factors were underpinned by an underlying culture in which prescribing is seen as a repetitive low-risk chore.

To reduce the risk of prescribing errors, a range of strategies addressing patient, task, individual, team and environment factors must be introduced.