CYP2C19 and macroglossia: We would hypothesize that in patients with a poor metabolizer phenotype characterized by reduced CYP2C19 activity, elevated drug metabolite levels disrupt autonomic vasoconstriction in the tongue (a highly neurovascular structure) and produce the characteristic macroglossia observed in these patients, though further serological and genotyping studies are required to draw definitive conclusions in this susceptible patient population.