Methylphenidate (Ritalin) supporters argue that the drug
hasn't been given a fair trial as treatment for adult
attention deficit hyperactivity disorder (ADHD) —
and it appears they may be right. A Harvard University
research group led by Dr Thomas Spencer published a study
in the March issue of Biological Psychiatry, which
suggests that the typical dose of methylphenidate (MPH)
at 0.6mg/kg/day — not the drug itself — may
be inadequate for adults.
The authors note "only modest improvement
in ADHD symptoms with MPH at the lower daily doses attained
after the first weeks of treatment." But they later
found that "an average oral daily dose of 1.1mg/kg/day
was consistently more effective than placebo ... suggesting
a dose-dependent response to treatment of adults with
ADHD." In addition, the response wasn't affected by
gender, social class, psychiatric co-morbidity or age.
Study results suggest that the
undertreatment of adult ADHD is a much bigger problem
and inadequate dosing is just the tip of the iceberg.
Most of the study participants had never been treated
as kids — the majority didn't receive any therapy
even as adults. In fact, despite having been symptomatic
since childhood, only 9% of the subjects reported any
previous treatment.
HISTORY
REPEATS ITSELF
A 1995 pilot study in the Archives of General Psychiatry
of 23 adult ADHD subjects by the same Harvard group
found a similar dose-related response to MPH. Marked
improvement was noted in patients receiving 1mg/kg/day
of immediate-release MPH as compared to placebo. The
positive effects were 50% greater than in studies using
0.6 mg/kg/day.
The group's most recently published
results are from a double-blind, randomized, six-week,
placebo-controlled study. This time around, the study
was much larger with 146 adults aged 19 to 60 enrolled.
All subjects met at least six of nine DSM-IV-R criteria
for ADHD, had a history of ADHD symptomatology from
childhood through adulthood and were moderately or severely
impaired due to ADHD.
Along with the noted effectiveness,
higher doses of methylphenidate were found to be "safe
and well tolerated," state the researchers in their
study. Adverse effects were similar to those reported
in children, including appetite suppression, dry mouth
and mild moodiness. While the authors caution that blood
pressure should be monitored during therapy, only an
increase in heart rate was seen in this study.
"The results confirm that MPH at
daily doses of up to 1.3mg/kg is a well tolerated and
effective treatment for adults with ADHD," notes the
Harvard team in its study. It is clear from its research
that more attention needs to be paid to the treatment
of adult ADHD.
Biol Psychiatry 2005, Mar
1;57(5):456-63
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