Methylphenidate, sold as Ritalin for treatment of attention-deficit hyperactivity disorder, causes changes to neurons in the reward areas of the brain similar to those seen in cocaine users, according to new research from the National Institute on Drug Abuse (NIDA).

Researchers gave lab mice injections of either methylphenidate or cocaine daily over the course of two weeks, then examined the reward areas of their brains. They found changes in dendritic spine formation, related to communication between nerve cells, and the expression of the protein delta Fos B, which is thought to be involved in the long-term action of addictive drugs.

The effects of the two drugs were not exactly the same, but there were significant similarities and overlap, researchers said. “Methylphenidate, which is thought to be a fairly innocuous compound, can have structural and biochemical effects in some regions of the brain that can be even greater than those of cocaine,” said lead researcher Yong Kim.

“Studies to date suggest that prescribed use of methylphenidate in patients with ADHD does not increase their risk for subsequent addiction. However, nonmedical use of methylphenidate and other stimulant medications can lead to addiction as well as a variety of other health consequences,” said NIDA Director Dr. Nora Volkow.

The study will be published in the Feb. 3, 2009 issue of the Proceedings of the National Academy of Sciences.