Restless legs syndrome and periodic leg movements in sleep: the primary role of dopaminergic mechanism.

We report here the possible effect of opiates on a patient exhibiting particularly severe restless legs syndrome (RLS) and periodic leg movements in sleep (PLMS). This patient was investigated in the sleep laboratory under three conditions, namely, unmedicated (baseline), medicated with codeine sulfate, and medicated with both codeine sulfate and pimozide. Codeine sulfate dramatically improved abnormal motor behavior in this patient. The addition of pimozide reversed the beneficial effect of codeine during the Forced Immobilization Test but not in spontaneous RLS or PLMS at night. These results are discussed in view of the possible involvement of the dopaminergic mechanism in RLS/PLMS syndrome.