Ondansetron treatment in patients with Tourette's syndrome

Ondansetron, a selective 5-HT₃ antagonist, may lower mesolimbic dopaminergic hyperactivity. The present open-label pilot study evaluated the effect of ondansetron in Tourette's syndrome. Six Tourette's syndrome men aged 14-48 years resistant to haloperidol participated in the study. Assessments included the Yale Global Tic Severity Scale (YGTSS), Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), and Tourette's syndrome-Clinical Global Impression (TS-CGI) scale. The maximal ondansetron dosage (8-16 mg per day) was given for 3 weeks. Ondansetron treatment was associated with a significant decrease in the severity of tics. Two patients showed a definite response (score improvement of 40% or more), and two showed a probable response (> 25%). Two patients did not improve. Side-effects were transient and included abdominal pain (n = 5) and constipation (n = 2). Ondansetron may possess anti-tic effects in some Tourette's syndrome patients.