Pathophysiology
Clinical meaning
The clinician prescribes ADHD medications based on evidence-based algorithms, selecting from stimulant and non-stimulant classes based on efficacy data, patient-specific factors, and risk-benefit analysis. Stimulant medications are first-line with the largest effect sizes (Cohen's d 0.8-1.0). Methylphenidate (MPH) blocks the dopamine transporter (DAT) and norepinephrine transporter (NET), increasing synaptic dopamine and norepinephrine concentrations in the prefrontal cortex. Available formulations: immediate-release (Ritalin, duration 3-4 hours), extended-release (Concerta/OROS delivery 10-12 hours, Biphentin bimodal 10-12 hours). Amphetamine-based agents (mixed amphetamine salts/Adderall, lisdexamfetamine/Vyvanse) both block DAT/NET reuptake AND promote vesicular release of dopamine and norepinephrine -- generally larger effect sizes but also more adverse effects. The clinician starts at the lowest available dose and titrates weekly based on symptom rating scales, functional improvement, and tolerability. Common adverse effects requiring monitoring: appetite suppression/weight loss (measure height and weight at each visit, plot on growth charts for children), insomnia (avoid afternoon dosing, consider melatonin), cardiovascular effects (baseline and periodic heart rate and blood pressure, ECG if cardiac history or family history of sudden death). Non-stimulant options: atomoxetine (SNRI, takes 4-6 weeks for full effect, monitor for...