Effect of haloperidol dose on iodine-123-IBZM brain SPECT imaging in schizophrenic patients.
Studies have suggested that antipsychotic drug therapy with haloperidol in schizophrenic patients requires an optimal dose that blocks the brain dopamine D2 receptors. We evaluated the effect of different doses of haloperidol on D2 receptor occupancy in schizophrenia.


METHODS
Three normal subjects and three patients with acute schizophrenia had serial brain SPECT imaging studies (every 5 min) for 3 hr following the injection of [123I]IBZM. The patients had IBZM studies off medication and at different doses (1-10 mg) of haloperidol.


RESULTS
The basal ganglia (BG) were well visualized in normals and in schizophrenics off medication. After haloperidol therapy, SPECT images showed qualitatively diminished activity in the basal ganglia. ROIs were drawn over the basal ganglia and cerebellum (CE). The results were expressed as BG/CE ratios. At 2 hr postinjection of IBZM, the mean BG/CE ratio in normals was 1.75 +/- 0.025. In schizophrenics, the BG/CE ratio off medication was 1.54 +/- 0.12. The BC/CE ratio showed an inverse relationship to haloperidol dose; 1.46 at 1 mg, 1.25 at 4 mg and 1.05 at 10 mg, respectively.


CONCLUSIONS
These results demonstrate that IBZM brain SPECT imaging studies are potentially useful to relate the antipsychotic drug D2 receptor occupancy with the administered dose in schizophrenic patients and may ultimately help optimize antipsychotic treatment.
Vallabhajosula
S
S
Department of Radiology, Mount Sinai Medical Center, New York, New York 10029, USA.
Hirschowitz
J
J
Machac
J
J
D000328:Adult; D014150:Antipsychotic Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D001479:Basal Ganglia / Q000000981:diagnostic imaging / Q000187:drug effects; D001549:Benzamides; D001921:Brain / Q000000981:diagnostic imaging* / Q000187:drug effects*; D002531:Cerebellum / Q000000981:diagnostic imaging / Q000187:drug effects; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D004305:Dose-Response Relationship, Drug; D005260:Female; D006220:Haloperidol / Q000008:administration & dosage* / Q000627:therapeutic use; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D011759:Pyrrolidines; D011877:Radionuclide Imaging; D017448:Receptors, Dopamine D2 / Q000032:analysis; D012559:Schizophrenia / Q000000981:diagnostic imaging / Q000188:drug therapy*
D014150:Antipsychotic Agents; D001549:Benzamides; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D007457:Iodine Radioisotopes; D011759:Pyrrolidines; D017448:Receptors, Dopamine D2; C055743:3-iodo-2-hydroxy-6-methoxy-N-((1-ethyl-2-pyrrolidinyl)methyl)benzamide; D006220:Haloperidol