EFFECTS OF THE D2 RECEPTOR AGONIST BROMOCRIPTINE ON SLEEP BRUXISM - REPORT OF 2 SINGLE-PATIENT CLINICAL-TRIALS

An altered dopamine receptor status has been associated with sleep bru xism. Evidence from a functional neuro-imaging study has implicated an abnormal side imbalance in striatal D2 receptor expression in its pat hophysiology. To assess the significance of this finding we studied th e effects of short-term administration of the preferential dopamine D2 receptor agonist bromocriptine on sleep bruxism in a double-blind, pl acebo-controlled polysomnographic and neuro-imaging study with a singl e crossover design. Six otherwise healthy and drug-free patients with sleep bruxism were entered into the trial. One of the patients dropped out due to an intercurrent illness, while three others were discontin ued from the study due to severe adverse reactions to bromocriptine. B ecause of the high frequency and intensity of the side-effects, the tr ial was interrupted. Two patients, however, completed the trial withou t any adverse reactions. Their outcome measures are presented as singl e-patient clinical trials. Following a two-week administration of brom ocriptine, both patients showed a decrease in the number of bruxism ep isodes pw hour of sleep of about 20% to 30% with respect to the placeb o. While no significant differences between both conditions (i.e., pla cebo and bromocriptine) were found for the number of bruxism bursts pe r episode, significantly lower root-mean-squared EMG levels per bruxis m burst occurred during bromocriptine use. In association with this po lysomnographically established attenuation of sleep bruxism, bromocrip tine afforded a decreased abnormal side distribution of striatal D2 re ceptor binding, as was evidenced by single-photon-emission computed to mography using the radioactive D2 receptor antagonist iodine-123-iodob enzamide. This study supports previous suggestions that the central do paminergic system may be involved in the modulation of sleep bruxism. To see if the present findings apply across a population, investigator s should use a peripheral D-2 antagonist to prevent side-effects.