Background: Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental condition marked by inattention, hyperactivity, and impulsivity. While stimulant medications are considered first-line treatment, their use is frequently limited by adverse effects such as appetite loss, insomnia, and gastrointestinal discomfort. This has prompted growing interest in adjunctive therapies that offer symptom relief with improved tolerability. Case Presentation: We report the case of a 17-year-old male with combined-type ADHD and poor tolerance to multiple stimulant and non-stimulant pharmacotherapies. The patient experienced significant side effects with high-dose extended-release methylphenidate (Jornay PM), necessitating discontinuation. Following the introduction of inositol (4g three times daily) alongside a reduced stimulant dose (60 mg), the patient exhibited substantial improvement in attention, impulse control, and emotional regulation, as measured by the Conners Rating Scale. Notably, these improvements occurred without the previously experienced gastrointestinal side effects. Discussion: Inositol, a glucose isomer involved in neurotransmitter signaling and receptor modulation, may influence dopaminergic and serotonergic pathways implicated in ADHD. Its neuroprotective and mood-stabilizing properties suggest potential as a safe adjunctive treatment, especially in cases with stimulant intolerance or emotional dysregulation. Conclusion: This case highlights the potential benefit of inositol as a well-tolerated adjunct to stimulant therapy in adolescents with ADHD. Further controlled studies are warranted to evaluate its efficacy and define its role in the broader management of treatment-resistant ADHD.
