Background: The introduction of the new oral anticoagulant drugs (NOACs) has recently been paid much attention. The main advantage of these drugs is that routine monitoring of the anticoagulant effects does not seem necessary.
Case description: A 53-year-old man who had just undergone partial knee arthroplasty went to the emergency department with shortness of breath and respiratory chest pain. The symptoms arose the day after thromboprophylaxis was switched from dalteparin 5000 IU QD to rivaroxaban 10 mg QD. The patient also used carbamazepine 600 mg BID for epilepsy. Based on a CT scan the patient was diagnosed with pulmonary embolisms. Use of carbamazepine, a CYP3A4 inducer, probably led to an increased clearance of rivaroxaban resulting in pulmonary embolisms.
Conclusion: We encourage monitoring of the anticoagulant effects of NOACs in case of drug-drug interactions, especially when NOACs are given in higher doses for a long period, in order to prevent treatment complications.