Paraxanthine

Paraxanthine, also called 1,7-dimethylxanthine, is a methylxanthine compound produced during the metabolism of caffeine. In humans it is the predominant primary caffeine metabolite. Most paraxanthine is formed in the liver when the enzyme CYP1A2 removes a methyl group from caffeine .¹

Because paraxanthine retains a xanthine structure similar to caffeine, it has pharmacological activity rather than being merely an inactive waste product. Like caffeine, it can influence adenosine signaling and has stimulant-related effects, although the potency, kinetics, and full physiological profile are not identical. Blood paraxanthine concentrations therefore reflect both prior caffeine exposure and the rate at which caffeine is metabolized .¹

Paraxanthine should not be treated as another name for caffeine. Caffeine is 1,3,7-trimethylxanthine, whereas paraxanthine is a distinct downstream molecule with one fewer methyl group. Other caffeine metabolites include theobromine and theophylline, but paraxanthine accounts for the largest share of primary caffeine metabolism in humans. Its effects and safety as an isolated ingested compound are a separate question from its normal formation after caffeine consumption .¹