Pharmacokinetics of theobromine and its metabolites in rabbits.

The pharmacokinetics of theobromine (3, 7-DMX) and its metabolites was investigated in detail in four male rabbits after bolus intravenous injection (4 mg/kg) of the compound. Apparent first-order rate constants for the metabolic processes involved in the formation of 3,7-DMX metabolites and their excretion in urine were calculated. Theobromine, 7-methylxanthine (7-MX) and 3-methylxanthine (3-MX) were measured in blood and urine, and the other metabolites were determined only in urine. An appropriate model of 14 compartments is formulated to describe the disposition of 3,7-DMX and its metabolites.