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Interpatient pharmacokinetic variability lower in patients receiving lisdexamfetamine as compared with mixed amphetamine salts

Thursday, December 13 2007 | Comments
Evidence Grade 0 What's This?
An analysis of 17 patients with attention-deficit/hyperactivity disorder who received either lisdexamfetamine dimesylate or an extended-release formulation of mixed amphetamine salts (MAS XR) shows that the interpatient variability of lisdexamfetamine is lower than that of MAS XR.

The study population came from a larger double-blind, randomized, crossover Phase II study of the efficacy and safety of lisdexamfetamine as compared with MAS XR and placebo. All participants were aged 6 to 12 years with ADHD combined or hyperactive/impulsive subtypes; their disorders had been diagnosed according to DSM-IV-TR criteria. The evaluable group for the purpose of the pharmacokinetic study consisted of 8 patients who received lisdexamfetamine 70 mg/day and 9 patients who received MAS XR 30 mg/d.

For the last visit of the double-blind period, blood was drawn from participants predose and at 1, 2, 3, 4.5, 6, 8, 10, and 12 hours postdose. Plasma samples were analyzed at a central laboratory. Quality control pools were also prepared.

In the lisdexamfetamine group, mean peak plasma levels of dextroamphetamine were achieved in 5.06 hours; in the MAS XR group, mean peak plasma levels were achieved in 6.56 hours. The mean maximum plasma concentration (Cmax) of dextroamphetamine in the lisdexamfetamine group was 155 ng/mL. In the MAS XR group, the mean Cmax of dextroamphetamine was 119 ng/mL.

The coefficient of variation (CV) for the Tmax values was 15.33% and 52.77% in the lisdexamfetamine and MAS XR groups, respectively. The CV for the Cmax values was 20.34% in the lisdexamfetamine group and 43.96% in the MAS XR group.

The investigators theorized that the lower level of interpatient variability in the lisdexamfetamine group may be due to "lisdexamfetamine being a prodrug ... not dependent on exogenous formulation/drug release delivery systems. Additional study would be helpful to further examine these findings." (Ermer JC, et al. Poster NR750.)

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