Test yourself: Did a drug interaction complicate this injury?
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 after a mechanical valve replacement 11 years ago, and has been recently diagnosed with depression.
A CT scan reveals a subdural haematoma and the patient’s INR measures 7.5.
Which of the following is most likely to increase the anticoagulant effect of warfarin? (Check the answer under the image)
- St John’s wort
Answer: 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.