Variations in dabigatran, rivaroxaban and warfarin drug interaction inclusion and severity level classifications among selected drug compendia

Purpose: This project sought to examine selected drug-drug interactions involving dabigatran, rivaroxaban and warfarin for both inclusion and variations in severity level classification among four commonly used online drug databases.

Methods: The James L. Winkle College of Pharmacy provides its faculty and students with access to four online drug compendia: Micromedex, E-Facts & Comparisons, Lexicomp and Clinical Pharmacology. In this analysis, 56 medications known to interact with either dabigatran or rivaroxaban were identified.  To determine whether these interactions were unique to dabigatran or rivaroxaban, warfarin was evaluated as a comparison agent.  Each of the four databases was evaluated for the presence of these interactions while assessing severity level classifications for any disparities. 

Results: The databases documented differing numbers of interactions and varying severity level classifications.  The number of documented dabigatran interactions in the databases ranged from 12/56 (21%) to 52/56 (93%).  Similar ranges were seen with rivaroxaban and warfarin.  Differences in severity level classification were difficult to assess due to these wide inclusion ranges.

Conclusion: Dabigatran and rivaroxaban are newer, oral anticoagulants with fewer drug interactions than warfarin.  Nevertheless, a number of drug interactions are similar for all three agents.  This evaluation demonstrated disparities both in interaction inclusion and in severity level classification.  It is therefore recommended that a clinician consult two or more compendia when making therapeutic decisions with these important medications.