Background Adverse events caused by drug-drug interactions (DDIs) can significantly contribute to mortality/morbidity during hospitalisation. Understanding the mechanisms of DDIs, working with our own data and adopting preventive measures may help reduce the risk.

Purpose The aim of the analysis was to asses the utility of the built-in DDI tool and identify drug combinations most frequently involved in serious DDIs in our hospital.

Material and methods The analysis was performed at a university hospital with 1127 beds. Retrospective analysis of inpatient electronic medication records with built-in DDI software from January 2015 to August 2015 was performed. The DDI data from these records were electronically extracted, and the top 10 drug pairs/groups most frequently involved in serious DDIs were identified. Only DDIs with the highest overall risk ratings (very serious or contraindicated) were taken into account. For comparison, risk rating by a trusted DDI tool (Lexi-Interact) was added. Subsequently, all medical records with occurrence of one of the top 10 DDIs were manually reviewed for details.

Results A total of 25 681 hospitalisation episodes were electronically analysed, and 809 serious DDIs were identified in 656 hospitalisation episodes. The top 10 most frequently involved DDIs represented 542 cases (67% of the DDIs identified). These top 10 drug pair/combinations were (in descending order) rilmenidine+β-blockers, clopidogrel+omeprazole, propafenone+β-blockers, clarithromycin+atorvastatin/simvastatin, amiodarone+metronidazole, amiodarone+citalopram, warfarin+metronidazole, amiodarone+simvastatin/lovastatin, clopidogrel+clarithromycin and verapamil+simvastatin. After detailed review and exclusion of false positive DDI signals, 249 DDI cases remained. 79% of the cases were managed appropriately and 21% were not respected, most frequently, the clopidogrel–omeprazole combination. In addition, of the 293 false positive DDI signals identified, 20% were misinterpreted.

Conclusion We identified the most frequent drug combinations involved in serious DDIs in our hospital and analysed them in detail. Although not flawless, the built-in DDI software proved to be a valuable tool for prevention of serious DDIs. Surprisingly, the omeprazole-clopidogrel DDI was relatively often ignored.

References and/or Acknowledgements We thank Pharm Dr Jana Duricova, PhD for help and consultations

No conflict of interest.