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Guanfacine XR effective, safe in treating ADHD in children, adolescents, researchers report

Wednesday, December 12 2007 | Comments
Evidence Grade 0 What's This?
Guanfacine extended release (XR) appears effective in treating children and adolescents with attention-deficit/hyperactivity disorder, according to data from a short-term study.

"Many individuals with ADHD do not respond to, cannot tolerate, or prefer alternatives to stimulant treatment," the authors of the study wrote.

Researchers conducted a double-blind, parallel-group, fixed-dose escalation study in which 345 children aged 6 to 17 years were randomized to receive placebo or guanfacine XR once daily in doses of 2 mg, 3 mg, or 4 mg. The study consisted of 3 periods, including a maximum 14-day screening period, a washout period that lasted approximately 1 week, and an 8-week treatment period. Drug doses were up-titrated at weekly visits in 1 mg increments to the randomized dose and tapered down in a similar fashion such that all subjects received a 1 mg dose during week 8.

Results showed that guanfacine XR-treated patients had a combined mean reduction in ADHD Rating Scale-IV (ADHD-RS-IV) scores of 16.7 points compared with a reduction of 8.9 points in the placebo group. The difference in ADHD-RS-IV scores between guanfacine XR-treated patients in all dose groups and those who received placebo was statistically significant at week 3 and remained so through week 5 (P<.001; the last assessment).

Ratings of "much" or "very much" improved on the Clinical Global Impression of Improvement (CGI-I) scale were observed in 55.95% of patients who received the 2 mg dose of guanfacine XR, 50% of those who received the 3 mg dose, and 55.56% of those who received the 4 mg dose compared with 25.64% of those who received placebo (P<.001 for all dose groups vs placebo).

Improvements in Parent Global Assessment test scores were observed in 62.12% of patients who received the 2 mg dose of guanfacine XR, 50.82% of those who received the 3 mg dose, and 66.1% of those who received the 4 mg dose compared with 23.08% of patients in the placebo group (P<.001 for 2 mg and 4 mg dose vs placebo; P=.0028 for the 3 mg dose vs placebo).

The authors noted that the duration of action of guanfacine XR in this trial supported a once-a-day dosing regimen and that effect sizes appeared to be proportional to the weight-adjusted dose.

The most commonly reported treatment-emergent adverse events were somnolence (32% of guanfacine XR-treated patients vs 4% of those who received placebo), fatigue (18% vs 4%, respectively), upper abdominal pain (14% vs 6%), and sedation (13% vs 4%). Forty-two guanfacine XR-treated patients (16.2%) withdrew due to adverse events compared with 1 patient (1.2%) in the placebo group. Mean decreases in pulse rate and blood pressure were modest, the authors added.

"[There were] no real surprises in [this] short-term trial," Dr. Raun Melmed, the lead researcher, told VerusMed. He also remarked that the effect size observed in this trial was encouraging. However, Dr. Melmed noted that there were some notable withdrawals in a longer-term trial of the drug caused by adverse effects, including sleep issues and tics. (Poster 104.)

This information concerns a use that has not been approved by the Food and Drug Administration.

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