The present study reports that azithromycin (AZT), a substrate for Mrp2, inhibited the in vitro and in vivo biliary as well as renal excretion of high-dose methotrexate (MTX). In contrast to results of hepatocyte in vitro study, the in vivo inhibition of MTX elimination occured within the clinically achievable AZT concentrations.
Therefore, the interaction between AZT and MTX can not be excluded in clinical settings.