Pharmacokinetics of SLI381 (ADDERALL XR), an extended-release formulation of adderall

Objective: To assess the pharmacokinetic (PK) properties of a single daily dose of Adderall® (mixed amphetamine salts) and the extended-release formulation, SLI381 (ADDERALL XR™), in pediatric attention-deficit/ hyperactivity disorder (ADHD). Method: Fifty-one children (aged 6-12 years) with ADHD participated in a 6-week, seven-visit, PK and pharmacodynamic study. PK sampling occurred during visit 1 and again at visit 7. At visit 1, subjects received an initial oral dose of SLI381, 20 mg. At visit 7 subjects completed 1 week of medication treatment following random assignment to once-daily orally dosed SLI381 10mg, 20 mg, or 30 mg; Adderall 10 mg; or placebo. Results: PK parameters evidenced substantial intersubject variability (coefficients of variation = 28-56%). Time to maximum concentration (T_max) for SLI381 versus Adderall showed average increases of 3.0 hours for dextroamphetamine (t = -2.35, p = .04, df = 8.6) and 3.2 hours for levoamphetamine (t = -2.39, p = .04, df = 9.2). The d- and l-isomer concentrations were highly correlated and approximated a 3:1 ratio. Conclusions: SLI381 showed extended T_max values compared with Adderall and appears suitable for once-daily dosing. Intersubject variability underscores the need for individual dose titration.