Purpose of study Initiatives to standardise hospital paper-based prescription charts are underway in various countries in an effort to reduce prescribing errors. The aim of this study was to investigate the extent to which prescribing error rates are influenced by prescription chart design and familiarity.

Study design In this prospective, randomised, cross-over study, Foundation Year 1 doctors working in five Scottish National Health Service (NHS) Boards participated in study sessions during which they were asked to prescribe lists of medications for five fictional patients using a different design of paper prescription chart for each patient. Each doctor was timed completing each set of prescriptions, and each chart was subsequently assessed against a predefined list of possible errors. A mixed modelling approach using three levels of variables (design of and familiarity with a chart, prescribing speed and individual prescriber) was employed.

Results A total of 72 Foundation Year 1 doctors participated in 10 data-collection sessions. Differences in prescription chart design were associated with significant variations in the rates of prescribing error. The charts from NHS Highland and NHS Grampian produced significantly higher error rates than the other three charts. Participants who took longer to complete their prescriptions made significantly fewer errors, but familiarity with a chart did not predict error rate.

Conclusions This study has important implications for prescription chart design and prescribing education. The inverse relationship between the time taken to complete a prescribing task and the rate of error emphasises the importance of attention to detail and workload as factors in error causation. Further work is required to identify the characteristics of prescription charts that are protective against errors.