Concentration-dependent inhibitory effects of baicalin on the metabolism of dextromethorphan, a dual probe of CYP2D and CYP3A, in rats

► Baicalin inhibited DXM O- and N-demethylase activity in rats liver microsomes. ► Baicalin decreased the CL of DXM, with a concomitant increase in the AUC in rats. ► Baicalin inhibited DXM metabolism in concentration-dependent manner in rats. ► Multiple doses of baicalin decreased DXM N-demethylase activity in an ex vivo study.