Warfarin (WF) shows a number of interactions with other drugs, which alter its anticoagulant effects. The albumin binding interaction is one such pharmacokinetic mechanism of drug interaction with WF, which induces a rise in the free WF concentration and thus increases the risk of WF toxicity. Teicoplanin (TEIC) is an anti-methicillin-resistant Staphylococcus aureus drug, which also binds strongly to albumin in the plasma. Therefore, co-administration of TEIC may displace WF from the albumin binding site, and possibly result in a toxicity. The present study was performed to investigate the drug-drug interaction between WF and TEIC in comparison with controls treated with vancomycin (VCM), which has the same spectrum of activity as TEIC but a lower albumin binding ratio.The records of 49 patients treated with WF and TEIC or VCM at Fukuoka University Hospital between 2010 and 2015 were retrospectively reviewed. These 49 patients consisted of 18 treated with TEIC in combination with WF, while 31 received VCM in combination with WF. Prothrombin time-international normalized ratio (PT-INR) showed a significant increase of 80.9 (52.0-155.3) % after co-administration of TEIC with WF. In contrast, the rate of PT-INR elevation associated with VCM plus WF was 30.6 (4.5-44.1) %. These observations suggested that TEIC can cause a rise in free WF concentration by albumin binding interaction. Therefore, careful monitoring of PT-INR elevation is necessary in patients receiving WF plus TEIC.
Keywords: albumin drug interaction; prothrombin time-international normalized ratio; teicoplanin; vancomycin; warfarin.