Background: Psychostimulants are considered first-line pharmacotherapy for youth with attention-deficit/hyperactivity disorder (ADHD), but questions remain regarding the comparative efficacy of amphetamine- and methylphenidate-based agents.
Objective: Our objective was to describe two acute randomized, double-blind, placebo-controlled, head-to-head studies of lisdexamfetamine dimesylate (LDX) and osmotic-release oral system methylphenidate (OROS-MPH) in adolescents with ADHD.
Methods: Adolescents (13-17 years) diagnosed with ADHD according to Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision (DSM-IV-TR) criteria were enrolled in an 8-week flexible-dose study [LDX 30-70 mg/day (n = 186 randomized); OROS-MPH 18-72 mg/day (n = 185 randomized); placebo (n = 93 randomized)] or a 6-week forced-dose study [LDX 70 mg/day (n = 219 randomized); OROS-MPH 72 mg/day (n = 220 randomized); placebo (n = 110 randomized)]. Attention-Deficit/Hyperactivity Disorder Rating Scale IV (ADHD-RS-IV) total score changes from baseline (primary endpoint) at week 8 (flexible-dose study) or week 6 (forced-dose study) were assessed with mixed-effects models for repeated measures. Secondary endpoints included improvement on the dichotomized Clinical Global Impressions-Improvement scale (CGI-I; key secondary endpoint) and changes from baseline on the ADHD-RS-IV subscales. Safety assessments included treatment-emergent adverse events (TEAEs) and vital signs.
Results: Least squares (LS) mean ± standard error of the mean (SEM) ADHD-RS-IV total score changes from baseline to end of treatment were -17.0 ± 1.03 with placebo, -25.4 ± 0.74 with LDX, and -22.1 ± 0.73 with OROS-MPH in the forced-dose study and -13.4 ± 1.19 with placebo, -25.6 ± 0.82 with LDX, and -23.5 ± 0.80 with OROS-MPH in the flexible-dose study. LS mean ± SEM treatment difference for the change from baseline significantly favored LDX over OROS-MPH in the forced-dose [-3.4 ± 1.04, p = 0.0013, effect size (ES) -0.33] but not the flexible-dose (-2.1 ± 1.15, p = 0.0717, ES -0.20) study. The percentage of improved participants on the dichotomized CGI-I at end of treatment was significantly greater with LDX than with OROS-MPH in the forced-dose study (81.4 vs. 71.3%, p = 0.0188) but not the flexible-dose study (LDX 83.1%, OROS-MPH 81.0%, p = 0.6165). The LS mean ± SEM treatment differences for change from baseline on the ADHD-RS-IV hyperactivity/impulsivity and inattentiveness subscales nominally favored LDX in the forced-dose study (hyperactivity/impulsivity subscale -1.3 ± 0.49, nominal p = 0.0081, ES -0.27; inattentiveness subscale -2.0 ± 0.63, nominal p = 0.0013, ES -0.33), but there were no significant differences between active treatments in the flexible-dose study. In both studies, LDX and OROS-MPH were superior to placebo for all efficacy-related endpoints (all nominal p < 0.0001; ES range -0.43 to -1.16). The overall frequency of TEAEs for LDX and OROS-MPH, respectively, were 66.5 and 58.9% in the forced-dose study and 83.2 and 82.1% in the flexible-dose study. TEAEs occurring in ≥ 5% of participants that were also reported at two or more times the rate of placebo were decreased appetite, decreased weight, insomnia, initial insomnia, dry mouth, and nasopharyngitis (LDX and OROS-MPH), irritability and dizziness (LDX only), and increased heart rate (OROS-MPH only) in the forced-dose study and decreased appetite, decreased weight, insomnia, and dizziness (LDX and OROS-MPH) and dry mouth and upper abdominal pain (LDX only) in the flexible-dose study. Mean ± standard deviation (SD) increases from baseline in vital signs (systolic and diastolic blood pressure, pulse) were observed in the forced-dose study [LDX 1.6 ± 9.65 and 3.3 ± 8.11 mmHg, 6.7 ± 12.78 beats per minute (bpm); OROS-MPH 2.6 ± 10.15 and 3.3 ± 9.13 mmHg, 7.6 ± 12.47 bpm] and the flexible-dose study (LDX 2.4 ± 9.46 and 2.8 ± 8.41 mmHg, 4.7 ± 11.82 bpm; OROS-MPH 0.4 ± 9.90 and 2.2 ± 8.64 mmHg, 6.0 ± 10.52 bpm) at the last on-treatment assessment.
Conclusions: LDX was superior to OROS-MPH in adolescents with ADHD in the forced-dose but not the flexible-dose study. Safety and tolerability for both medications was consistent with previous studies. These findings underscore the robust acute efficacy of both psychostimulant classes in treating adolescents with ADHD. CLINICALTRIALS.