High levels of dopamine D2 receptor occupancy with low-dose haloperidol treatment: a PET study

OBJECTIVE: The purpose of this study was to determine the dopamine D2 receptor occupancy induced by low-dose haloperidol treatment in a prospective trial. METHOD: Seven patients with schizophrenia were treated with 2 mg/day of haloperidol for 2 weeks, and D2 receptor occupancy was measured by 11Craclopride and positron emission tomography. RESULTS: The patients showed high levels of D2 occupancy (53%-74%); five of them showed substantial clinical improvement, and none showed important side effects. CONCLUSIONS: The findings demonstrate that low doses of haloperidol induce D2 receptor occupancies that are in the putative therapeutic range. In combination with recent empirical trials, these findings should encourage clinicians to initiate treatment of psychotic episodes with low (2-4 mg haloperidol equivalent) doses of typical neuroleptics, particularly for first-episode patients.