title: A probable clinically significant interaction between warfarin and cloxacillin: three case reports.
abstract: METHODS
  Three patients were admitted to the Imam Hospital, Tehran, Iran with a diagnosis of bacterial endocarditis. The patients had indications for valve replacement surgery and anticoagulant therapy. The administration of cloxacillin reduced the effect of warfarin, and subsequent increases in warfarin doses were unable to overcome this effect.
  
  
  CONCLUSIONS
  A decrease in warfarin anticoagulation effects was detected in our three patients following cloxacillin therapy for infective endocarditis. Penicillinase-resistant penicillins remain essential antibiotics in the treatment of severe infections caused by Staphylococcus aureus due to their bactericidal activity, safety, and cost. Thus, in situations where anticoagulants are indicated in patients with infective endocarditis, it would be better to replace warfarin with low-molecular-weight or unfractionated heparin.
authors.affiliation: Department of Clinical Pharmacy, Faculty of Pharmacy, Tehran University of Medical Sciences, PO Box 14155/6451, Tehran 1417614411, Iran. khalilih@tums.ac.ir
authors.forename: Hossein
authors.initials: H
authors.lastname: Khalili
authors.forename: Naemeh
authors.initials: N
authors.lastname: Nikvarz
authors.forename: Farhad
authors.initials: F
authors.lastname: Najmeddin
authors.forename: Simin
authors.initials: S
authors.lastname: Dashti-Khavidaki
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000009:adverse effects*; D000925:Anticoagulants / Q000009:adverse effects* / Q000493:pharmacokinetics; D001777:Blood Coagulation / Q000187:drug effects*; D003023:Cloxacillin / Q000009:adverse effects*; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods; D004697:Endocarditis, Bacterial / Q000188:drug therapy*; D005260:Female; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008943:Mitral Valve / Q000601:surgery*; D014859:Warfarin / Q000009:adverse effects* / Q000493:pharmacokinetics; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D000925:Anticoagulants; D014859:Warfarin; D003023:Cloxacillin