Improving prescribing using a rule based prescribing system.

OBJECTIVE: To test the hypothesis that the prescribing behaviour of doctors would improve after having experience with a computerised rule based prescribing system.
DESIGN: A prospective observational study of changes in prescribing habits resulting from the use of a computerised prescribing system in (1) a cohort of experienced users compared with a new cohort, and (2) a single cohort at the beginning and after 3 weeks of computer aided prescribing.
SETTING: 64 bed renal unit in a teaching hospital. INTERVENTION: Routine use of a computerised prescribing system by doctors and nurses on a renal unit from 1 July to 31 August 2001. MAIN OUTCOME MEASURES: Number of warning messages generated by the system; proportion of warning messages overridden; comparison between doctors of different grades; comparison by doctors' familiarity with the system.
RESULTS: A total of 51,612 records relating to 5995 prescriptions made by 103 users, of whom 42 were doctors, were analysed. The prescriptions generated 15,853 messages, of which 6592 were warning messages indicating prescribing errors or problems. Doctors new to the system generated fewer warning messages after using the system for 3 weeks (0.81 warning messages per prescription v 0.42 after 3 weeks, p = 0.03). Doctors with more experience of the system were less likely to generate a warning message (Spearman's rho = -0.90, p = 0.04) but were more likely to disregard one (Spearman's rho = -1, p<0.01). Senior doctors were more likely than junior doctors to ignore a warning message.
CONCLUSIONS: Doctors are influenced by the experience of using a computerised prescribing system. When judged by the number of warning messages generated per prescription, their prescribing improves with time and number of prescriptions written. Consultants and registrars are more likely to use their clinical judgement to override warning messages regarding prescribed drugs.