March 3, 2006

ADHD stimulant may be less subject to abuse

An MGH research team has found that a delayed-release stimulant used to treat ADHD may be less likely to be abused than other stimulant drugs. Study participants taking therapeutic oral doses of Concerta — a once-daily form of the drug methylphenidate — did not report perceiving and enjoying the drug's effects, features that are associated with a medication's potential for abuse. The report appears in the March 2006 issue of The American Journal of Psychiatry.

"We know that drugs that cause euphoria are potentially abusable, and euphoria requires rapid delivery to the brain. Using sophisticated PET scan imaging, we were able to examine the rate of delivery of both rapid- and delayed-release formulations of methylphenidate and correlate those results with how the drugs felt to study volunteers," says Thomas Spencer, MD, of the MGH Pediatric Psychopharmacology Unit, the paper's lead author.

The study compared a traditional, quick-release form of the drug with Concerta, a formulation that produces a gradual increase in blood levels over 12 hours. A combination of blood tests, participant questionnaires and PET scans of the medication's target areas in the brain found that few of those receiving delayed-release methylphenidate reported detecting or enjoying the drug's activity, while most of those receiving the immediate-release form were aware of and enjoyed the drug's effects. These differences were seen even though the peak blood and brain levels of both drugs were comparable.

"The ability to show that the rate of brain drug delivery may determine abuse potential is important to our understanding of the safety of different formulations," says Spencer. His MGH co-authors are Joseph Biederman, MD, Bertha Madras, PhD, and Darin Dougherty, MD, of Psychiatry; and Ali Bonab, PhD, Elijahu Livni, PhD, and Alan Fischman, MD, PhD, of Radiology.