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)

• Bupropion
• St John’s wort
• Fluoxetine
• Phenelzine

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.

To see more images like this, see Figure1