Disposition of methamphetamine and its metabolite amphetamine in brain and other tissues in rats after intravenous administration.
These studies characterized the concentration-time profile of (+)-methamphetamine [(+)-METH] and its metabolite (+)-amphetamine [(+)-AMP] in the brain and five other tissues after (+)-METH administration. Male Sprague-Dawley rats received a pharmacologically active (+)-METH i.v. bolus dose (1.0 mg/kg) or a nonpharmacologically active s.c. infusion (20 h at 1.2 mg/kg/day). Tissues (n = 3 per time point) were collected for more than four elimination half-lives in the i.v. group, or at a single steady-state time point (20 h) in the s.c. group. Based on data from the area under the concentration-time curves after i.v. dosing, the rank order of (+)-METH tissue accumulation was kidney > spleen > brain > liver > heart > serum with terminal elimination half-life values ranging from 53 to 66 min. (+)-METH concentrations were highest at the first measured time point (2 min) in all tissues except the spleen, which peaked at 10 min. The brain-to-serum concentration ratio rose from 7:1 at 2 min to a peak of 13:1 at 20 min before equilibrating to a constant value of 8:1 at 2 h. Following s.c. (+)-METH dosing, the (+)-METH brain-to-serum concentration ratio was the same as the equilibrated ratio following i.v. dosing. (+)-AMP concentrations peaked at 20 min in all tissues before decaying with terminal elimination half-life values ranging from 68 to 75 min. Analysis of the area under the concentration-time curve molar amounts of (+)-AMP and (+)-METH showed that (+)-AMP accounted for approximately one-third of the drug tissue exposure over time. Thus, these data indicate the importance of both (+)-METH and (+)-AMP in pharmacological effects following i.v. (+)-METH administration.
Rivière
G J
GJ
Department of Pharmacology, College of Medicine, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA.
Gentry
W B
WB
Owens
S M
SM
D000661:Amphetamine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D007275:Injections, Intravenous; D007279:Injections, Subcutaneous; D008297:Male; D008694:Methamphetamine / Q000008:administration & dosage / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
D008694:Methamphetamine; D000661:Amphetamine