Phenprocoumon Carbamazepine

A 53-year-old woman taking phenprocoumon had a large reduction in prothrombin time when carbamazepine was added. After withdrawal of carbamazepine, the prothrombin time returned to target values. Valproate had no effect on phenprocoumon. 

Schlienger R, Kurmann M, Drewe J, MuUer-Spahn F, Seifritz E. Inhibition of phenprocoumon anticoagulation by carbamazepine. Eur Neuropsychopharmacol 2000 10(3) 219-21. 

The anticoagulant effects of warfarin can be markedly reduced by carbamazepine, and two case reports surest phenprocoumon is similarly affected. Oxcarbazepine appears not to interact significantly with warfarin. 

---