An open-label trial of OROS methylphenidate in adults with late-onset ADHD

Many adults with current impairing symptoms of attention-deficit/hyperactivity disorder (ADHD) do not report an age at onset before 7 years of age and cannot, therefore, be assigned the full Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), diagnosis of ADHD. We hypothesized that treatment with oral release osmotic system (OROS) methylphenidate (MPH) will be safe and efficacious for the treatment of adults with late-onset ADHD.

This was a 6-week, open-label, prospective treatment study of OROS MPH monotherapy in 36 adult patients with late-onset ADHD (onset later than the required 7 years of age) using standardized instruments for diagnosis and a robust oral daily dose of up to 1.3 mg/kg/day. Symptom severity was assessed with the Adult ADHD Investigator Symptom Report Scale (AISRS) and the Clinical Global Impression (CGI) scale.

Subjects reported robust current symptoms of ADHD at pre-treatment baseline (11.1+/-2.8 DSM-IV symptoms), but had an atypical mean age at onset of 14.2+/-8.6 years. Treatment with OROS MPH at an average daily dose of 78.2+/-29.4 mg was associated with a statistically and clinically significant reduction in ADHD symptoms relative to baseline as assessed through the AISRS (-16.4+/-10.5; P<.001). Using a categorical definition of response (CGI-I much or very much improved), a majority (n = 26; 72%) of subjects were rated as improved at endpoint.

These results extend previous findings in adults with full ADHD to adults meeting criteria for late-onset ADHD and support the need for further controlled clinical trials in this population.