Azathioprine and Acenocoumarol Drug Interaction in Patients with Crohn’s Disease: A Case Report

Background: Acenocoumarol is an anticoagulant with numerous drug reactions. We report here, an unusual interaction between acenocoumarol and azathioprine. Case Presentation: A 35-year-old woman, treated with acenocoumarol for thrombosis of the superior mesenteric vein, was prescribed azathioprine for Crohn’s disease. Three days later, INR values decreased from 2.36 to 1.48. The dose of acenocoumarol had to almost be doubled to reach an INR value of 2.56. The interaction between azathioprine and acenocoumarol was then suspected. Few similar cases of interactions between azathioprine and another coumarin derivative, warfarin, have been reported. To our knowledge, this is the second case of such interaction reported with acenocoumarol in literature. Conclusion: Thus, despite the rarity of this interaction reporting, we draw attention to the importance of close monitoring of INR values in patients treated with acenocoumarol associated with azathioprine.