Methylphenidate

Dose-dependent. Most pronounced during the hours of peak medication effect. Typically results in reduced lunch intake in children on ER formulations. Can lead to clinically meaningful weight loss in some patients. Management: take medication with or after breakfast, provide high-calorie snacks during wear-off, ensure adequate dinner intake. Monitor weight trends, not individual measurements.

Related to sympathomimetic activation persisting into evening. Worse with late dosing or long-acting formulations. Strategies: earlier dosing, shorter-acting formulations, melatonin, adjunctive clonidine/guanfacine at bedtime. Consider that untreated ADHD itself disrupts sleep, the inability to "turn off" racing thoughts is a common ADHD sleep complaint independent of medication.

Typically modest (average increase 2-6 bpm heart rate, 2-4 mmHg blood pressure). Monitor periodically. Clinically significant in patients with pre-existing cardiovascular conditions. Obtain baseline vital signs before starting and monitor at each visit during titration.

More frequent during titration. Usually resolves within the first weeks of treatment. Rarely requires medication change.

This is a critical clinical distinction:

End-of-dose rebound: Irritability, emotional lability, or worsening ADHD symptoms occurring as the medication wears off (typically late afternoon for ER formulations). The child is fine during the medication's peak and becomes irritable, tearful, or oppositional as it clears. This is a pharmacokinetic problem (the brain adjusting to the sudden drop in catecholamine support), not overmedication. Management: add a small IR booster dose in the afternoon, switch to a longer-acting formulation, or adjust timing.

Overmedication irritability: Irritability, emotional constriction, or rigidity occurring during peak medication effect. The child appears tense, joyless, or "wound too tight" while the medication is active. This reflects being on the right side of the inverted-U curve (too much catecholamine stimulation in the PFC). Management: reduce the dose.

Confusing these two patterns leads to opposite prescribing errors: increasing the dose for rebound (correct) vs increasing the dose for overmedication (harmful). Ask when the irritability occurs relative to dosing to distinguish them.

Monitor height and weight at every visit. Approximately 1-2 cm reduction in predicted adult height over years of treatment in most studies. The clinical significance of this modest reduction must be weighed against the substantial academic, social, and psychological benefits of ADHD treatment. Drug holidays may partially mitigate growth effects but interrupt symptom management.

Monitor at every visit. Tic exacerbation does not automatically require stimulant discontinuation; the clinical significance of the tics must be weighed against the ADHD treatment benefit. The older belief that stimulants are contraindicated in tic disorders has been largely revised. Alpha-2 agonists (guanfacine, clonidine) are an alternative that can treat both ADHD and tics.

Patients may appear "flat," overly quiet, or "not themselves." This is a sign of overmedication, not an expected therapeutic effect. Reduce the dose. If it occurs at the minimum effective dose, consider switching to the other stimulant class or a non-stimulant. The "zombie" concern parents raise is about this side effect, it is real, recognizable, and treatable with dose adjustment.

New hallucinations, paranoia, or delusions at therapeutic doses. Occurs in approximately 0.1-0.2% of pediatric patients in large cohort studies. More common in children than adults. Requires immediate discontinuation and evaluation. Resolves with medication removal. Not indicative of a primary psychotic disorder, though it should prompt careful reassessment of the diagnostic picture. This is a board-tested topic: the correct answer is always to stop the stimulant, not to add an antipsychotic or increase the dose.