FRIDAY, March 3 (HealthDay News) -- A delayed-release formulation of methylphenidate used to treat attention-deficit/hyperactivity disorder accumulates more slowly in the blood and the brain and may have a lower potential for abuse, according to a study in the March issue of the American Journal of Psychiatry.
Thomas J. Spencer, M.D., of Massachusetts General Hospital in Boston, and colleagues assessed dopamine receptor occupancy by positron emission tomography as well as drug plasma levels in 12 normal adults. The subjects were given either 40 mg of immediate-release or 90 mg of delayed-release oral methylphenidate on two separate occasions. Participants also completed an hourly questionnaire on whether they were aware of the drug's effects and the likeability of the formulations.
Compared with immediate-release methylphenidate, maximum plasma concentration and maximum central nervous system dopamine receptor occupancy were achieved later with the delayed-release methylphenidate. The researchers also found no awareness or likeability for the delayed-release formulation.
"The findings suggest that the abuse potential of oral methylphenidate is strongly influenced by the rate of delivery and not solely by the magnitude of plasma concentration or brain transporter occupancy," Spencer and colleagues conclude.
The study was funded by the National Institute of Mental Health and McNeil Consumer and Specialty Pharmaceuticals.
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