Test Predicts ADHD Response to Ritalin

June 22, 2004 -- Ritalin and other stimulant drugs don't help everyone with ADHD. Now it looks as though brain scans can predict who will benefit and who won't.

ADHD -- attention deficit hyperactivity disorder -- isn't just for kids. People who suffer from this common problem often get help from stimulant drugs such as Ritalin. But not all cases of ADHD are alike. Some people simply don't respond to the drugs.

Doctors think that many ADHD cases stem from a problem with a brain chemical called dopamine. Indeed, Ritalin ups brain levels of dopamine. It does this by blocking a transporter molecule that carries dopamine away from nerve endings.

In earlier studies, Christian la Fougere, MD, and colleagues at the University of Munich, Germany, injected people with a marker compound that made the dopamine transporter light up during brain scans. They found that untreated adults with ADHD had significantly more of these transporter molecules than normal adults.

In their current study, la Fougere's team used the same dopamine-transporter marker technique to look at 18 adults with ADHD. Before Ritalin treatment, 13 of the 18 patients showed high levels of the dopamine transporter. All but one of these patients had significant improvement in symptoms with Ritalin.

The remaining five ADHD patients had low levels of the dopamine transporter and got no relief from Ritalin.

La Fougere and colleagues reported their findings at the 51st annual meeting of the Society of Nuclear Medicine, held this week in Philadelphia.

"Our first results indicate that measurement of dopamine transporters may be an important prognostic predictor of therapy response to [Ritalin]," the researchers note in their presentation abstract.

SOURCE: Society of Nuclear Medicine 51st Annual Meeting, Philadelphia, June 19-23, 2004.