A 7-year-old boy is brought to the paediatric clinic by his mother with complaints of inattention and hyperactivity at school for the past 18 months. The teacher reports that he cannot sit still during class, frequently interrupts peers, and loses his school supplies. At home, he is impulsive, talks excessively, and has difficulty completing homework despite normal intelligence. Physical examination is unremarkable. The child's father has a history of similar behavioural problems in childhood. Psychometric testing shows normal IQ. What is the most appropriate first-line pharmacological intervention for this child?

Explanation

## Diagnosis and Management of ADHD ### Clinical Presentation Recognition **Key Point:** This child meets DSM-5 criteria for ADHD, Combined Presentation: - Symptoms of inattention (loses supplies, difficulty completing tasks) - Symptoms of hyperactivity-impulsivity (cannot sit still, talks excessively, interrupts) - Duration ≥6 months - Onset before age 12 - Functional impairment across settings (school and home) - Normal intelligence excludes intellectual disability ### First-Line Pharmacological Treatment **High-Yield:** Stimulant medications (methylphenidate and amphetamines) are the first-line pharmacological agents for ADHD in children. **Clinical Pearl:** Methylphenidate is preferred as the initial stimulant choice because: 1. Extensive safety and efficacy data in paediatric populations 2. Shorter half-life allows for flexible dosing and easier titration 3. Lower abuse potential compared to amphetamines 4. Predictable pharmacokinetics with multiple formulations available (immediate-release, extended-release) ### Mechanism of Action Methylphenidate blocks the reuptake of dopamine and noradrenaline at the presynaptic terminal, increasing their availability in the prefrontal cortex and striatum—regions critical for executive function, attention, and impulse control. ### Treatment Algorithm ```mermaid flowchart TD A[ADHD Diagnosis Confirmed]:::outcome --> B[Psychoeducation & Behavioural Intervention]:::action B --> C{Adequate Response?}:::decision C -->|No| D[Initiate Stimulant: Methylphenidate]:::action C -->|Yes| E[Continue Behavioural Management]:::outcome D --> F{Tolerability & Efficacy?}:::decision F -->|Good| G[Continue & Monitor]:::action F -->|Poor/Adverse effects| H[Switch to Amphetamine or Atomoxetine]:::action ``` ### Why Other Options Are Not First-Line | Agent | Role in ADHD | Reason Not First-Line | |-------|--------------|----------------------| | **Fluoxetine** | SSRI; used for comorbid depression/anxiety | Not effective for core ADHD symptoms; used as adjunct only | | **Risperidone** | Atypical antipsychotic | Reserved for comorbid aggression, tics, or psychotic features; not first-line monotherapy | | **Atomoxetine** | Non-stimulant; noradrenaline reuptake inhibitor | Second-line option if stimulants contraindicated or ineffective; slower onset | **Key Point:** Behavioural interventions (parent training, school-based interventions) should ALWAYS accompany pharmacotherapy, not replace it. [cite:DSM-5 ADHD Criteria; Harrison 21e Ch 473]