Deuterium isotope effects on caffeine metabolism.

The aim of this work was to study the influence of labelling on caffeine metabolism according to the incubation mode. It has been observed that labelling induces an isotopic effect on metabolisation speed: apparent half-lives are systematically increased. Moreover, isotopic effects are in agreement with those previously observed for retention times. Qualitatively, caffeine labelling systematically induces metabolic variations to the detriment of the metabolic pathway that induces the loss of the trideuteromethyl group. Caffeine accumulation and the release of the main metabolites have been studied with respect to isotopic effects on crossing the cell membrane. It has been demonstrated that, in most of the cases, accumulation decreased and that either metabolite release was increased or no isotopic effect was observed.