Clozapine Therapy and Increases in Homovanillic Acid

K and colleagues¹ reported that increases in the cerebrospinal fluid (CSF) homovanillic acid (HVA) to 5-hydroxyindoleacetic acid (5-HIAA) ratio (HVA/HIAA ratio) are correlated with antipsychotic response to haloperidol treatment in patients with schizophrenia or schizoaffective disorder. In their study, haloperidol treatment was associated with significant increases in both CSF HVA concentrations and the CSF HVA/5-HIAA ratio, while CSF 5-HIAA concentrations were unchanged. Of interest, only the increase in the CSF HVA/ 5-HIAA ratio was correlated with antipsychotic response.

We have been studying the relationship of CSF HVA and 5-HIAA concentrations to antipsychotic response with the "atypical" neuroleptic clozapine. We² and Szymanski et al³ previously have reported the replication of the original findings of Pickar et al⁴ that showed a low pretreatment CSF HVA/5-HIAA ratio is more likely to be associated with clinical response to clozapine in patients unresponsive to "typical" neuroleptics.

We now report preliminary