Category: drug_metabolism
Caffeine (1,3,7-trimethylxanthine) clears via three parallel N-demethylations by CYP1A2: N3-demethylation to paraxanthine (~84%, the dominant pathway), N1-demethylation to theobromine (~12%), N7-demethylation to theophylline (~4%). Paraxanthine is itself a CNS stimulant + adenosine receptor antagonist, and is partly responsible for caffeine's late-half-life effects. The 84:12:4 ratio plus a 5-7 h plasma t½ are the basis for the caffeine + paraxanthine plasma profile.