A marked increase in the effects of warfarin, sometimes accompanied by bleeding, has been seen in a small number of patients also given azithromycin
, or roxithromycin, but most patients seem unlikely to develop a clinically important interaction. This interaction has also been seen in a few patients taking acenocoumarol or phenprocoumon with either clarithromycin
, or roxithromycin.
Very few patients appear to have a clinically significant interaction. Any interaction appears to develop over the first 7 days (so note interactions may occur after an antibacterial treatment course has finished). It has been suggested that those taking relatively low doses of anticoagulant are most at risk. Consider increasing the frequency of INR monitoring.