LA JOLLA, CALIF. – Children and adults with chronic tic disorders who were treated with levodopa did not experience a worsening of tics, Dr. Mollie Gordon reported during a poster session at the annual meeting of the American Neuropsychiatric Association.
Treated patients did experience significant improvements in attention and hyperactivity symptoms.
“I think this challenges the way we think about the dopamine pathways in the brain,” Dr. Gordon, of the department of psychiatry at Washington University School of Medicine, St. Louis, said in an interview. “We've always thought of Tourette as being in a sense an excess of dopamine that affects children with movement disorders and causes them to tic and have other sequelae. So when we block the dopamine, these patients do better. What we've shown here is that if we give them dopamine, we would expect them to get worse, since the medicines we've been using block dopamine. But they don't.”
In an 8-week pilot study, Dr. Gordon and her associates randomly assigned 12 children and 18 adults with Tourette syndrome or chronic tic disorder to receive 12.5 mg of carbidopa, 50 mg of levodopa, or matched placebo capsules. The researchers recorded tic severity, clinical status, and side effects at baseline, 4 weeks, and 8 weeks. Instruments used included the Yale Global Tic Severity scale, video recordings of tics, the Clinical Global Impressions scale, the Global Assessment of Functioning scale, and various questionnaires.
The researchers found that tic severity did not increase in patients who took levodopa. Patients who took levodopa also experienced improvements in attention and hyperreactivity symptoms (a 17% improvement vs. no improvement for those on placebo), and the drug was not associated with any significant side effects.
Limitations of the study as stated in the poster include the fact that serum prolactin did not decrease appreciably in patients who took levodopa and that the “limited number of subjects may have reduced statistical significance of any effect.”
Dr. Gordon hopes that future studies will shed more light on the pathophysiology of dopamine regulation. “We know that these patients have a dopamine abnormality in the brain,” she said. “If it's not a matter of being too much or too little [dopamine], the question is, how do we figure out what's wrong? Do these drugs affect auto inhibitory receptors? Is there something going on in the brain that has to do with the dopamine dysregulation? If we [have] more information about the pathophysiology of these diseases, then we can figure out the best management.”
The study was funded in part by the Tourette Syndrome Association.