Pharmacokinetic, pharmacological, and genotoxic evaluation of deuterated caffeine.

Altering caffeine's negative physiological effects and extending its duration of activity is an active area of research; however, deuteration as a means of achieving these goals is unexplored. Deuteration substitutes one or more of the hydrogen atoms of a substance with deuterium, a stable isotope of hydrogen that contains an extra neutron. Deuteration can potentially alter the metabolic profile of a substance, while maintaining its pharmacodynamic properties. d9-Caffeine is a deuterated isotopologue of caffeine with the nine hydrogens contained in the 1, 3, and 7 methyl groups of caffeine substituted with deuterium. d9-Caffeine may prove to be an alternative to caffeine that may be consumed with less frequency, at lower doses, and with less exposure to downstream active metabolites of caffeine. Characterization of d9-caffeine's genotoxic potential, pharmacodynamic, and pharmacokinetic behavior is critical in establishing how it may differ from caffeine. d9-Caffeine was non-genotoxic with and without metabolic activation in both a bacterial reverse mutation assay and a human mammalian cell micronucleus assay at concentrations up to the ICH concentration limits. d9-Caffeine exhibited a prolonged systemic and brain exposure time in rats as compared to caffeine following oral administration. The adenosine receptor antagonist potency of d9-caffeine was similar to caffeine.