Paraxanthine, also known as 1,7-dimethylxanthine, is an isomer of theophylline and theobromine, two well-known stimulants found in coffee, tea, and chocolate mainly in the form of caffeine.

[10] Paraxanthine is a selective inhibitor of cGMP-preferring phosphodiesterase (PDE9) activity[11] and is hypothesized to increase glutamate and dopamine release by potentiating nitric oxide signaling.

[13] Paraxanthine is a competitive nonselective phosphodiesterase inhibitor[14] which raises intracellular cAMP, activates PKA, inhibits TNF-alpha[15][16] and leukotriene[17] synthesis, and reduces inflammation and innate immunity.

[19] The pharmacokinetic parameter for paraxanthine are similar to those for caffeine, but differ significantly from those for theobromine and theophylline, the other major caffeine-derived methylxanthine metabolites in humans (Table 1).

(t1/2; hr) (Vss,unbound; l/kg) (CL; ml/min/kg) Paraxanthine is a phosphodiesterase type 9 (PDE9) inhibitor and it is sold as a research molecule for this same purpose.