Drug level of d- and l-amphetamine during intravenous self-administration

Rats were allowed to self-administer dextro and levo isomers of amphetamine in doses of 0.25, 0.50, 0.75 and 1.0 mg/kg/injection for 6 h/day. Total body level of drug was calculated at the time of responding for each drug injection. Body level of amphetamine initially increased and then decreased (0–2 h), and thereafter remained relatively constant for the remainder of the experimental session (2–6 h). During 2–6 h of self-administration, calculated whole body levels of both d- and l-amphetamine remained relatively constant across injection doses. In another study, blood was removed several times during 2–6 h at the time of responding for drug injection. Again, no difference in blood level of ¹⁴C-amphetamine was found across a range of injection doses. Mean blood levels were 0.48 g/ml for l-amphetamine and 0.18 g/ml for d-amphetamine. Drug intake averaged 2.0 mg/kg/h for l-amphetamine and 0.79 mg/kg/h for d-amphetamine.