AbstractAim. To comparein vitrometabolism rates for artemisinin and the CYP2B6 substrates, bupropion, propofol and efavirenz in human liver microsomes.Methods. Rate constants of artemisinin, bupropion, propofol and efavirenz metabolism by human liver microsomes from a panel of 12 donors, with different levels of CYP2B6 activity, were estimated in WinNonlin. Correlations between the metabolic rate constant for artemisinin and the other CYP2B6 substrates were examined.Results. Artemisinin and propofol depletion data in human liver microsomes were described by first order kinetic models. For bupropion and efavirenz, metabolite formation data were incorporated in the model. Rate constants varied considerably for all substrates. There was a high degree of correlation of rate constants between substrates (r⩾0.87,p<0.001).Conclusions. The rate ofin vitrometabolism of artemisinin was correlated significantly to that of bupropion, propofol and efavirenz, suggesting artemisinin to be a potential alternative marker to assess CYP2B6 activity. Further studies characterizing the metabolic fate of artemisinin are needed in order to evaluate its utility as anin vitroandin vivoCYP2B6 probe substrate, since CYP2B6 might not be the only CYP isoform involved in the depletion of artemisinin. Copyright © 2009 John Wiley & Sons, Ltd.