paraxanthiin

Paraxanthiin, more commonly spelled paraxanthine (chemical name 1,7-dimethylxanthine), is a dimethylxanthine and a primary metabolite of caffeine in humans. It is produced in the liver by cytochrome P450–mediated demethylation of caffeine and typically accounts for a large proportion of caffeine’s metabolic products.

Pharmacologically, paraxanthine is an active compound with stimulant properties. It acts as an antagonist at adenosine receptors, similar to caffeine, and has been associated with increased locomotor activity, enhanced alertness, and modulation of neurotransmitter release. Paraxanthine also influences peripheral processes such as lipolysis, leading to elevated free fatty acid levels in plasma. Compared with caffeine, some effects of paraxanthine appear to be qualitatively similar but quantitatively different, and it may contribute substantially to the overall physiological response to ingested caffeine.

Research on paraxanthine has explored its role in caffeine’s effects, its pharmacokinetics, and potential differential effects on cardiovascular and central nervous systems. Safety and toxicity data are limited relative to caffeine itself; observed effects depend on dose and individual metabolism. Paraxanthine continues to be of interest in neuropharmacology and toxicology as a marker of caffeine metabolism and as an active metabolite that helps explain caffeine’s varied effects in humans.