Theophylline has no advantages over caffeine as a putative model drug for assessing CYP1A2 activity in humans

Abstract

In summary the theophylline 6 h plasma and 0-12 h urine ratios 1MU/13DMX and 3MX/13DMX, both reflecting N-demethylation seem to be predictors of the CYP1A2 mediated metabolism of theophylline, whereas only the plasma ratio correlated with the caffeine plasma 17DMX/13TMX ratio. Thus, it would appear that the plasma theophylline N-demethylation ratios are superior to the urine ratios as indices of CYP1A2 activity. However, because in some individuals the concentrations of theophylline metabolites in plasma were close to the limit of detection, it is concluded that theophylline does not have marked advantages over caffeine as a model drug for assessing CYP1A2 activity.