Clonidine in the treatment of Tourette syndrome: a review of data.

There are conflicting data concerning the efficacy of clonidine in TS. Some TS patients, probably 50% or more, experience substantial, long-term symptomatic improvement with minimal side effects. However, their profile of response is often variable, with behavioral symptoms appearing to show the most consistent improvement. Maximal benefit may not be evident for 4 to 6 months. A minority of patients do not respond, and a few worsen on clonidine. The need for additional double-blind trials is clear. Additional metabolic and pharmacologic investigations are needed to understand the determinants of the response of TS patients to clonidine. The response to acute doses of clonidine on sedation, growth hormone release, blood pressure, and plasma MHPG levels may be predictive of eventual therapeutic response. The variable response to clonidine, however, suggests that noradrenergic mechanisms in TS may not be of primary pathogenic importance. The study of interactions between neurochemical systems may help illuminate the pathophysiology of TS and lead the way to improved treatment of this disabling condition.