Quetiapine Warfarin

Rogers T, de Le i J, Atcher D. Possible interacticn between warfarin and quetiapine. J Clin Psychojjharmacol 999) 19,382-3. 

A case report describes a woman taking warfarin who developed a raised INK when quetiapine was started. 

The reasons for this apparent interaction are not known but the authors suggest that the quetiapine may have inhibited the metabolism of the warfarin (possibly by competitive inhibition of the cytochrome P450 isoenzymes CYP3A4 and CYP2C9), thereby increasing its effects. They also suggest that the phenytoin may have had some part to play. This is only an isolated case but bear it in mind in the case of an unexpected response to concurrent use. 

---