Agomelatine Augmentation in an Adult Patient With ADHD, Insomnia, and Waning Response to Lisdexamfetamine: A Case Report

Agomelatine is a melatonergic MT1/MT2 receptor agonist and serotonin 5-HT2C receptor antagonist with potential effects on sleep regulation and prefrontal catecholamine signaling. This CARE-style clinical case report describes a 32-year-old woman with attention-deficit/hyperactivity disorder, insomnia, and a perceived waning response to lisdexamfetamine despite adherence to treatment. Agomelatine 25 mg nightly was added to her existing stimulant regimen. Following initiation, the patient reported improved sleep continuity, better daytime concentration, and a perceived restoration of stimulant benefit. Her Insomnia Severity Index score improved from 19 to 9 during follow-up. Liver function tests were monitored throughout treatment and remained within normal limits, and no clinically significant adverse effects were reported. This case suggests that agomelatine may be considered as a monitored adjunct in selected patients with ADHD, insomnia, and reduced perceived stimulant benefit. However, causality cannot be established from a single case, and further controlled studies are needed.