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Stimulant dosing in adults with ADHD lower than effective levels

Wednesday, December 12 2007 | Comments
Evidence Grade 0 What's This?
Dosing of stimulants for adults with attention-deficit/hyperactivity disorder appears to fall well below dose ranges that have been shown to be optimally effective in trials of adults with ADHD, according to a new study.

Researchers used service and pharmacy claims from the PharMetrics database from 2000 to 2004 to identify patients aged 18 to 64 years who were treated for ADHD with OROS methylphenidate (n=3,089), mixed amphetamine salts (MAS) extended release (n=2,225), methylphenidate immediate release (n=2,531), or MAS immediate release (n=3,431). They evaluated the initial and maximum dosing patterns of the drugs and the demographic and clinical characteristics of the patients.

Overall, most prescriptions were from physicians other than psychiatrists in each of the treatment groups. Specifically, 35.9% of those in the OROS methylphenidate group received the stimulant from a psychiatrist, whereas 44.0% of both the methylphenidate IR and MAS IR groups and 44.6% of the MAS XR group received the respective drugs from a psychiatrist.

Mean initial daily doses were 31.2 mg/day for OROS methylphenidate, 26.8 mg/d for methylphenidate IR, 20.3 mg/d for MAS XR, and 23.5 mg/d for MAS IR. The initial dose was not significantly associated with the patient's age, but it was significantly higher for male patients than for female patients in all treatment groups.

The patients who were treated by psychiatrists had significantly higher mean initial doses than did those treated by other physicians in all groups except the methylphenidate IR group.

Mean maximum daily doses were 39.9 mg/d for OROS methylphenidate, 32.1 mg/d for methylphenidate IR, 26.1 mg/d for MAS XR, and 30.0 mg/d for MAS IR. For the 2 amphetamine-based groups, the youngest age group had significantly lower daily maximum doses relative to the middle-aged group. For the MAS XR group, the youngest age group also had significantly lower maximum doses than did the oldest age group (P<.01). For the methylphenidate IR and MAS IR groups, the male patients had significantly higher mean maximum doses than did the female patients.

The patients who were treated by psychiatrists had significantly higher maximum doses relative to those treated by other physicians in all groups but the OROS methylphenidate group.

Most of the patients reached their maximum daily dose on the first stimulant prescription (OROS methylphenidate, 62.7%; methylphenidate IR, 74.0%; MAS XR, 63.4%; MAS IR, 67.2%).

Being aged 36 to 50 years was independently associated with higher maximum doses relative to younger adults for the OROS methylphenidate and MAS IR groups. For the MAS XR group, being aged 36 to 50 years or aged 51 to 64 years was associated with higher doses relative to the youngest group.

Male sex was associated with higher maximum stimulant doses relative to female sex for all groups but the OROS methylphenidate group. For the MAS XR and MAS IR groups, treatment by a psychiatrist was independently associated with higher maximum doses than was treatment by other physicians.

"In community practice, stimulant dosing in the management of ADHD in adult patients falls well below dose ranges reported to be optimally effective in clinical trials of adult ADHD," the authors wrote.

"For each of the 4 stimulants studied, mean maximum daily doses prescribed were approximately half of the doses associated with robust efficacy in clinical trials," they added. (Olfson M, et al. Poster 208.)

This information concerns uses that have not been approved by the Food and Drug Administration.

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