Q: 52 year old female with previous history of Atrial fibrillation admitted with new onset seizure after hemodialysis. CT scan is negative and there is no deficit. Neurology thinks it may be due to metabolic derangement. Phenytoin (Dilantin) is started after loading dose. Next day patient develop severe GI bleed. What could be the reason?

Hint: Its drug interaction question


Answer: Patient is probably on warfarin for her A. fib. and Phenytoin increases effects of warfarin. Actual basis of interaction is unknown.

The Multidisciplinary Medication Management Project (joint collaboration of the American Society of Consultant Pharmacists and the American Medical Directors Association) - lists phenytoin and warfarin among its top 10 drug interactions.