Pharmacokinetics of lisdexamfetamine dimesylate and its active metabolite, d-amphetamine, with increasing oral doses of lisdexamfetamine dimesylate in children with attention-deficit/hyperactivity disorder: a single-dose, randomized, open-label, crossover study.
BACKGROUND
Lisdexamfetamine dimesylate (LDX) is a long-acting oral prodrug stimulant indicated for the treatment of attention-deficit/hyperactivity disorder (ADHD) in children 6 to 12 years old and in adults. Information on the pharmacokinetic profile of LDX in children with ADHD is lacking.


OBJECTIVE
The aim of this study was to assess the pharmacokinetic properties of d-amphetamine delivery from LDX, and intact LDX with increasing doses of LDX administered in children with ADHD.


METHODS
This single-dose, randomized, open-label, 3-period crossover study was conducted in children aged 6 to 12 years with ADHD symptoms that adversely affected school performance and required a medication switch. Eligible patients had prior stimulant experience, with good tolerability. Patients were administered a single oral dose of LDX 30, 50, or 70 mg in a randomized sequence. Each study period was separated by a 6-day washout. The pharmacokinetic properties of d-amphetamine and intact LDX were calculated over 48 hours. Adverse events (AEs) were assessed using physical examination, including vital sign measurements, and ECG.


RESULTS
The study enrolled 18 children (mean [SD] age, 9.6 [1.9] years [range, 6-12 years]; 56% boys; weight, 36.0 [7.6] kg; 44% white, 44% black). Mean (%CV) C(max) values of d-amphetamine postdose were 53.2 (18.1), 93.3 (19.5), and 134.0 (19.4) ng/mL with LDX 30, 50, and 70 mg, respectively (T(max), approximately 3.5 hours). These findings suggest that the overall AUC for d-amphetamine was dose proportional. The intact LDX AUC was 10% to 20% higher in girls than in boys, and for d-amphetamine was <10% higher. The most commonly reported AEs, of 17 total cases, with 30-, 50-, and 70-mg LDX were anorexia (4 [22%], 7 [41%], and 8 [47%], respectively), elevated blood pressure (2 [11%], 1 [6%], and 3 [18%]), and abdominal pain (2 [11%], 2 [12%], and 2 [12%]). All AEs were mild or moderate. No serious AEs were reported. One child was withdrawn from the analysis because of pharyngitis considered to be unrelated to LDX use.


CONCLUSION
The findings from this study in a small, select population of children with ADHD suggest that the concentrations of d-amphetamine, the active metabolite of LDX, after single-dose administration of LDX at increasing doses appeared to be dose proportional and had low interpatient variability.