Child Psychiatry — Adverse Effects of Stimulants in ADHD
A 14-year-old boy with attention-deficit/hyperactivity disorder started immediate-release methylphenidate 10 mg twice daily 4 weeks ago, with clear improvement in school. He now has reduced appetite at lunch, has lost 2 kg and takes over an hour to fall asleep. His mood is good and he enjoys his usual activities. Heart rate is 84 beats/min, and full blood count and thyroid function are normal. What is the most likely explanation?
- A.Expected adverse effects of methylphenidateCorrect
- B.Undiagnosed hyperthyroidism
- C.Emerging major depressive disorder
- D.Poor dietary habits during adolescence
Explanation
Reduced appetite, weight loss and delayed sleep onset are the most common adverse effects of stimulant medication and typically appear within the first weeks of treatment. Methylphenidate suppresses appetite most strongly around the peak of each dose, which is why lunchtime intake falls, and an afternoon dose can delay sleep onset. The timing here, beginning soon after starting the drug in a boy whose attention has improved, makes the medication the obvious link. Hyperthyroidism can cause weight loss and insomnia, but it usually increases appetite and causes tachycardia, and normal thyroid function excludes it. Depression can disturb sleep and appetite, but he has preserved mood and interest. Management does not require stopping a medication that is working: give doses with or after meals, offer a substantial breakfast and evening meal, move the second dose earlier or reduce it, and review sleep hygiene. Height, weight, heart rate and blood pressure should be recorded before treatment and monitored regularly, with height checked every 6 months and weight every 3 months in children aged 10 or under, or at 3 and 6 months after starting and then 6-monthly in older children. Persistent weight loss or a fall across growth centiles warrants dose reduction, a planned break or switching to a different medication.
Why each option
- A.
- Correct. Appetite suppression, weight loss and delayed sleep onset are the commonest stimulant adverse effects and began after starting methylphenidate.
- B.
- Hyperthyroidism usually increases appetite and heart rate, and his normal thyroid function tests exclude it as the cause.
- C.
- Depression can disturb sleep and appetite, but his preserved mood and enjoyment of activities argue strongly against it.
- D.
- Dietary habits do not explain the close timing with starting methylphenidate or the combination with new difficulty falling asleep.
Reference: NICE NG87 Attention deficit hyperactivity disorder: diagnosis and management 2018 (updated 2019); AAP Clinical Practice Guideline for ADHD 2019; UpToDate — Pharmacology of drugs used to treat ADHD in children and adolescents
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