Distribution profile of 2,5-dimethoxy-4-bromoamphetamine (DOB) in rats after oral and subcutaneous doses

2,5-Dimethoxy-4-bromoamphetamine (DOB) is one of the potent hallucinogenic phenylalkylamines, whose ingestion has already caused several deaths reported all over the world. However, there is unsufficient information on DOB properties based on controlled pharmacokinetic studies available. The aim of this study was to clarify the distribution profile of DOB and its phenolic metabolite 2-methoxy-5-hydroxy-4-bromoamphetamine (2M5H4BA) in blood and biological tissues of experimental rats. The rats were administered a 20 mg/kg dose of DOB·HCl by oral ingestion or subcutaneous injection. Plasma and brain, liver and lung tissues were collected at 0.5, 1, 2, 4, 8, 16, and 32 h after dosing (three animals per time point). The samples were prepared by a liquid–liquid extraction procedure and the extracts were assayed by GC–MS. After per oral application, DOB peak plasma level of 320 ng/mL was reached after one-hour post dosing as well as 2M5H4BA peak concentration of 203 ng/mL. A rapid phase of DOB absorption, 2M5H4BA formation and their tissue distribution during the first two hours after application were followed by a slow decrease rate of the elimination process until 32 h. After subcutaneous application, high plasma levels of the unchanged parent drug and relatively reduced formation of its metabolite 2M5H4BA were observed. DOB maximum plasma concentration of 1143 ng/mL was reached after one-hour post application, whereas its metabolite peak level after 8 h was 213 ng/mL. The concentration profiles of both compounds in plasma after per oral and subcutaneous administration revealed the existence of significant first pass effect after per oral administration that significantly affected DOB bioavailability. DOB tissue concentrations exceeded plasma and the highest values were found in the lungs, where drug accumulation occurred with prolonged retention till 32 h after subcutaneous dose. Although the plasma/tissue transfer was more effective for the lipophilic parent drug than for its hydroxylated metabolite 2M5H4BA, the metabolite tissue levels were significant. The hallucinogenic potential of 2M5H4BA appearing in brain remains unclear as nothing is known about its pharmacological activity at present.