Trials of pharmacological interventions for Tourette syndrome: A systematic review

Introduction: Gilles de la Tourette Syndrome (GTS) is a childhood-onset hyperkinetic movement disorder defined by the chronic presence of multiple motor tics and at least one vocal tic and often complicated by co-morbid behavioural problems. The pharmacological treatment of GTS focuses on the modulation of monoaminergic pathways within the cortico-striato-thalamo-cortical circuitry. This paper aims to evaluate the efficacy and safety profiles of pharmacological agents used in the treatment of tics in patients with GTS, in order to provide clinicians with an evidence-based rationale for the pharmacological treatment in GTS. Method: In order to ascertain the best level of evidence, we conducted a systematic literature review to identify double-blind randomised controlled trials of medications in GTS populations. Results: We identified a large number of pharmacological agents as potentially effective in improving tic symptoms. The alpha-2 agonist Clonidine is amongst the agents with the most favourable efficacy-versus-adverse events ratio, especially in patients with co-morbid attention-deficit hyperactivity disorder, although effect sizes vary evidence-based studies. Discussion: Our results are in line with the findings of uncontrolled open-label studies. However, most trials have low statistical power due to the small sample sizes, and newer agents, such as Aripiprazole, have not been formally tested in double-blind randomised controlled trials. Further research should focus on better outcome measures, including Quality of Life instruments.