Transition from methylphenidate or amphetamine to atomoxetine in children and adolescents with attention-deficit/hyperactivity disorder - A preliminary tolerability and efficacy study

Background: The primary treatment for attention-deficit/hyperactivity disorder (ADHD) has been psychostimulants. Recently developed nonpsychostimulant treatments have allowed certain patients to switch from a psychostimulant to a nonpsychostimulant. However, the outcomes of such switches have not been systematically studied. Objective: The purpose of this pilot study was to assess treatment tolerance and efficacy during a crosstaper transition from methylphenidate or amphetamine to atomoxetine among children and adolescents with ADHD. Methods: This pilot study was conducted in patients (aged 6-17 years) with incomplete responses (failure to obtain full reduction/elimination of symptoms) or intolerance of adverse events (AEs) during psychostimulant treatment. Patients continued ongoing psychostimulant treatment during the first week of the study. Transition to atornoxetine began by administering atomoxetine 0.5 mg/kg.d plus full-close psychostimulant for 1 week, followed in the second week by 1.2 mg/kg.d atomoxetine plus half-dose psychostimulant. Patients remained on 1.2 mg/kg.d atomoxetine monotherapy for the remaining 5 weeks. This stepwise transition was enacted due to the difference in pharmacodynamics between the psychostimulants and atomoxetine. Applying a stepwise cross-titration allowed for better control of ADHD symptoms during the intervening period. Change in ADHD symptoms, as measured by the mean change in the Attention-Deficit/Hyperactivity Disorder Rating Scale-IV-Parent Version: Investigator-administered and -scored (ADHDRS-IV-Parent: Inv), was assessed from baseline to end point. Results: Of the 62 subjects enrolled in the study, 39 (62.9%) were diagnosed as ADHD-combined type. Similar proportions were receiving methylphenidate (51.6%) and amphetamine (48.4%). Slightly more wished to switch due to inadequate response (53.2%) than intolerability (46.8%). Nine subjects discontinued at various times during the course of the study (patient or parent/caregiver decision [4], AE [2], protocol violation [2], and lack of efficacy [1]). Mean (SD) ADHDRS-IV-Parent:Inv total scores (n = 59, lastobservation-carried-forward) improved significantly from baseline (visit 2) to an end point (32.1 [10.5] vs 22.6 [14.0]; P < 0.001). Of the 58 subjects answering in the atomoxetine monotherapy phase, 38 (65.5%) reported a preference for atomoxetine treatment over their previous psychostimulant. Tolerability results were as follows: 26 (44.1%) of 59 patients reported >= 1 AE, the most common being somnolence (4 [6.8%]), fatigue (3 [5.1%]), decreased appetite (3 [5.1%]), cough (3 [5.1%]), headache (3 [5.1%]), and contact dermatitis (2 [3.4%]). No clinically severe AEs were reported. Both mean (SD) diastolic (2.4 [7.8] mm Hg; P = 0.031) and systolic (2.4 [7.9] mm Hg; P = 0.029) blood pressures increased significantly from baseline to end point. Electrocardiography revealed a significant increase in mean (SD) heart rate (9.2 [11.6] bpm; P < 0.001) and a corresponding decrease in mean (SD) RR interval (-77.8 [98.2] ms; P < 0.001). Statistically significant, but mild, increases in diastolic pressure and heart rate were observed. Conclusion: These children and adolescent patients were successfully switched from methylphenidate or amphetamine to atomoxetine treatment, with resulting improvement in ADHD symptom severity from baseline in this pilot study.