Acute elevation of liver function test values following concomitant administration of dabigatran and primidone.

Purpose: We report a unique case of transiently elevated liver function test (LFT) values associated with concurrent use of dabigatran and primidone, which has not previously been described in the scientific literature.

Summary: Management of drug-drug interactions requires a fundamental understanding of pharmacodynamic and pharmacokinetic parameters. Despite the use of available best predictive models, idiosyncratic drug reactions may still occur when a newly approved medication begins to be used in the general population. We report a case of a possible interaction (Naranjo adverse drug reaction probability score of 3, Roussel Uclaf causality assessment method score of 3) between dabigatran and primidone in a 70-year-old Caucasian male resulting in a transient elevation of LFT values. The patient was transitioned from warfarin to dabigatran in the setting of persistently subtherapeutic international normalized ratio values. During a routine outpatient follow-up appointment approximately 1 month after dabigatran initiation, the patient was discovered to have LFT values greater than 5 times the upper limit of normal. Dabigatran was thus discontinued; the patient was returned to warfarin therapy and their LFT values returned to baseline.

Conclusion: Studies have indicated a potential for reduced dabigatran efficacy with concurrent use of primidone due to P-glycoprotein induction, thereby potentiating the risk for thrombosis. To date, reports of this interaction resulting in hepatic injury are lacking. The present case suggests that this interaction may be clinically significant with regard to selection of antithrombotic medication therapy in patients on primidone therapy.