NEW YORK (Reuters Health) – Clonidine in the form of extended-release tablets improves response to psychostimulant treatment in children and adolescents with attention-deficit/hyperactivity disorder, results of a phase III trial indicate.
Clonidine is increasingly used in combination with stimulants to treat ADHD, Dr. Scott H. Kollins, at Duke University Medical Center in Durham, North Carolina; and colleagues explain in the June issue of Pediatrics. However, only two small clinical trials with immediate-release clonidine have been undertaken.
For the current study, the researchers tested extended-release clonidine versus placebo added to baseline stimulant treatment (ie, methylphenidate or amphetamine) in 198 children and adolescents with hyperactive- or combined-subtype ADHD, who had an inadequate response to their stable stimulant regimen.
During the 8-week treatment period, dosing could be adjusted up or down depending on response, but after week 5 the extended-release clonidine dose was tapered to the lowest allowable dose.
After 5 weeks, the change from baseline in the total ADHD Rating Scale IV score was -15.7 in the clonidine-plus-stimulant group compared with -11.5 in the placebo-plus-stimulant group (p=0.009), the investigators report.
Similarly, the corresponding changes in a standardized parent rating scale were -40.2 vs -27.1 (p=0.017), and for the Clinical Global Impression of Severity score the changes were -1.5 vs -1.2 (p=0.021), the team found.
During the final 3-week tapering phase, the ADHD score worsened in both groups, but the between-group difference remained significant, according to the report.
Adverse effects thought to be related to treatment, such as somnolence and headache, occurred in 45% of the clonidine group and 41% of the placebo group. Also, there were no clinically relevant differences in corrected QT intervals between the two groups, Dr. Kollins and colleagues note.
Summing up, they conclude, “The results of this study suggest that (extended-release clonidine) in combination with stimulants is useful in reducing ADHD in children and adolescents with partial response to stimulants.”
Pediatrics 2011;127:e1406–e1413
