A 76-year-old male presents with a progressive headache, dizziness, and confusion after falling from his bed the night before. He currently takes warfarin following a mechanical valve replacement 11 years ago, and has been recently diagnosed with depression. A CT scan reveals a subdural hematoma and the patient’s INR measures 7.5.
Selective serotonin reuptake inhibitors (SSRIs) such as fluoxetine may inhibit the metabolism of warfarin and increase its anticoagulant effect. It is suggested that patients on antidepressants have their INR closely monitored.