Effectiveness of computerised alerts to reduce drug–drug interactions (DDIs) and DDI-related harm in hospitalised patients: a quasi-experimental controlled pre–post study

Background Drug–drug interaction (DDI) alerts target the co-prescription of two potentially interacting medications and are a frequent feature of electronic medical records (EMRs). There have been few controlled studies evaluating the effectiveness of DDI alerts. This study aimed to determine the impact of DDI alerts on rates of DDIs and on associated patient harms.

Methods Quasi-experimental controlled pre–post study in five Australian hospitals. Three hospitals acted as control hospitals (EMR with no DDI alerts) and two as intervention (EMR with DDI alerts). Only DDI alerts at the highest severity level (defined as ‘major contraindicated’) were switched on at intervention hospitals. These alerts were not tailored to clinical context (ie, patient, drug). A total of 2078 patients were randomly selected from all patients (adult and paediatric) admitted to hospitals 6 months before and 6 months after EMR implementation. A retrospective chart review was performed by study pharmacists. The primary outcome was the proportion of admissions with a clinically relevant DDI. Secondary outcomes included the proportions of admissions with a potential DDI and with DDI-related harm.

Results Potential DDIs were identified in the majority of admissions (n=1574, 74.7%) and clinically relevant DDIs identified in half (n=1026, 48.7%). DDI alerts were associated with a reduction in the proportion of admissions with potential DDIs (adjusted OR (AOR)=0.38 (0.19, 0.78)) but no change in clinically relevant DDIs (AOR=1.12 (0.68, 1.84)) or in DDI-related harm (AOR=2.42 (0.47,12.31)). 199 DDIs (76 at control and 123 at intervention hospitals) for 35 patient admissions were associated with patient harm, and 2 patients experienced severe DDI-related harm pre-EMR implementation.

Discussion Implementation of DDI alerts, without tailoring alerts to clinical context, is unlikely to reduce patient harms from DDIs. Organisations should reconsider implementation of DDI alerts in EMRs where significant tailoring of alerts is not possible. Future research should focus on identifying safe, efficient and cost-effective ways of refining DDI alerts, so expected clinical benefits are achieved, and negative consequences of excessive alerting are minimised.