Response to levodopa challenge in Tourette syndrome.

A dopaminergic excess has been commonly postulated in the pathophysiology of tics, and an early report described acute worsening of tics with levodopa. However, dopamine agonists sometimes improve tics. We undertook this pilot study to determine whether people with tics could tolerate an acute dose of levodopa. Six adults with Tourette syndrome (TS) who had never been treated with neuroleptics took 150 mg levodopa by mouth under single-blind conditions after carbidopa pretreatment. All six subjects reported a decrease in self-rated tic severity (mean -40%, p <0.05), and three spontaneously asked if they could be prescribed levodopa for chronic treatment. Blinded videotape ratings of motor tic severity improved by 37% (p <0.02). A large, placebo-controlled trial will be required to confirm these findings, which raise important questions concerning the relationship of tic expression to dopaminergic activity.