Clonidine - A critical review of its role in the treatment of psychiatric disorders

Clonidine is an imidazoline compound that was originally used as an antihypertensive agent. It has been found to reduce sympathetic tone via an agonist action at central alpha(2) adrenergic receptors, as well as agonist effects on central imidazoline receptors. Clonidine has sedative properties, and its use has been explored by both researchers and clinicians in the treatment and investigation of psychiatric disorders that have a pathophysiology that may involve adrenergic mechanisms. Clonidine has been used extensively in a number of psychiatric disorders, including mood, anxiety, substance abuse, childhood-onset and movement disorders, narcolepsy and anorexia nervosa, and as a treatment for the adverse effects of other drugs. However, there have been few double-blind, controlled studies of the drug in any of these conditions. The disorders for which the use of clonidine is most well supported by research are opiate dependence and Gilles de la Tourette's syndrome. It may also play a limited role in the treatment of patients who have certain disorders that are refractory to standard treatments, and as an adjunctive agent in patients with only a partial response to standard agents. In addition, the drug is currently being used increasingly as a probe of the noradrenergic system in patients with anxiety disorders, depression or schizophrenia. Clonidine is generally well tolerated in patients with psychiatric disorders, although its use is limited by dose-dependent sedative and hypotensive effects.