[Acute pharmacological test of clonidine in essential tremor]

Thirty-seven patients with essential tremor were given intramuscular clonidine injections of 0.3 mg. Physical examination and statistical analysis showed that response was highly positive (t = 13.47; p < 0.0001) 60 min after administration. The absence of peripheral alpha-adrenergic receptors for tremor suggest that the drug acts centrally, consistent with the theory that essential tremor originates in a central oscillating pacemaker.