Abstract
Introduction: Attention deficit/hyperactivity disorder (ADHD) is the commonest childhood neuro-developmental disorder. Methylphenidate (MPH) is a psychostimulant commonly prescribed in clinical practice to treat patients with ADHD. Comorbidity of Type 1Diabetes mellitus (T1D) and ADHD in children can be encountered in clinical practice. However, the impact of MPH on the blood glucose profile is scarcely addressed in the literature.
Methods: Multiple blood glucose concentrations (BGCs) obtained from a 12 years old male with T1D (under treatment with continuous insulin infusion) and comorbid ADHD have been evaluated after having received 2 dose levels (5 mg and 7.5 mg) methylphenidate (MPH). BGCs were assessed at 6 time points, over 3 weeks period. During the assessment periods, the patient had similar daily feeding en activity conditions and unchanged background insulin infusion The means of the values obtained after each dose level were compared with each other and with those obtained before commencement of MPH treatment.
Results: Three clinically relevant findings were encountered. The mean values of fasting Blood glucose levels (BGLs) obtained during MPH treatment periods were lower than that obtained before MPH use, respectively -28% and -23% below BL for the 5 and 7.5 mg dose levels. The means of other post-MPH treatment values obtained, through the day, were higher than that obtained before treatment, respectively +39% and +40% above Base line (BL). In addition, increasing MPH dose level was associated with increased BGL at all assessment time points.
Conclusion: Methylphenidate seems to dysregulate blood glucose levels in patients with type 1 diabetes mellitus. This might lead to serious consequences, including both microvascular and macrovascular diseases, particularly in vulnerable subjects such as those who receive medication for a long period of time. Commencement of treatment with and up-titration of MPH dose in ADHD patients with comorbid T1D requires close monitoring of blood glucose concentrations to avoid potential blood glucose excursions that might lead to unwanted complications.

Key words: Methylphenidate, ADHD, Type 1 Diabetes Mellitus