Potential Drug Interactions with Coumadin (Warfarin) and Prozac (Fluoxetine): A Brief Report and Review of the Literature

We were askedto see a woman with recurrent depression and a history ifdeep vein thrombosis. (Consultation and L iaison Service). She had been started initially on Prorac (fluoxetine) and was secondarily started on Coumadin (uiaifarin). The patient presented with severe bruising if both lower extremities. We were asked to investigate the case to determine if a drug interaction with Prozac had produced the problem. A review if the world's literaturefai led to produce a report ifa drug interaction between Prozac and Coumadin producing a bleeding disorder. Scrutiny ifthis case could not produce evidence that this occurred. A retrospective analysis if 4 additional cases was performed. None ifthesepatients requiredadjustment iftheir Coumadin while on Prozac. It would be reasonable to assume that as th e mean age of th e U nited States population rises , th e inciden ce of como rbid medi cal a nd psychi a tric d isease is incr easing. Patients a re oft en pr escribed medi cations whi ch may int eract with psychotropic drugs . Second-generation ant idepressants a re ge ne ra lly cons idered safe drugs in th e medi call y ill popu lation because of their minimal a n t icho linerg ic properties and fewer adverse sid e effec ts. Fo r th e ph ysician , a kn owled ge of drug interactions with th e most com monly prescribed psychotropic medi cations is not only helpful , but should be th e standard of ca re. Recen tly, we were asked to see a woman with recurrent depression a nd a history of deep vein thrombosis . Sh e had been initially s tar te d on Prozac (fluoxe t ine ) an d was secondarily started on Co umad in (warfarin) . The pat ient pr esent ed with seve re bru ising of both lower ex t re mi t ies and a seco ndary cellu litis . An added com plica ting fact was that she had a Di ptheria , Pertussis, T et anus vaccination 3 weeks prior to ad mission. Bot h ce llulitis and th e D.P.T. vaccin at ion pot entially int e rfere with coag ula t ion. On admission her Proth rom bin Tim e (PT) was 50 a nd Part ial Thromb oplastin Time (PTT) was 100, a sce nario more cons iste nt with a coagulopa thy rather than Coumadin toxicity. When as ked to consult on this case , we had to investigat e th e possibil ity of Prozac interact ing wit h Coumadin. The Ph ysicia ns Desk Reference ca u tions agains t coa d ministe r ing th e two drugs . (I)