Feedback for A 10-year-old boy with a diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD) has been treated with methylphenidate for the past three months. Despite an adequate trial at therapeutic doses, he continues to experience significant symptoms of inattention, hyperactivity, and impulsivity that interfere with his school performance and social interactions. Additionally, he has experienced intolerable side effects such as decreased appetite and difficulty sleeping. According to NICE guidelines, what would be the most appropriate next step in his management?