Korean Journal of Biological Psychiatry

Selective serotonin reuptake inhibitors(SSRIs), as haloperidol, are metabolized in the cytochrome P450IID6. They can cause inhibition of metabolism of antipsychotics to elevate the serum level of antipsychotics and exacerbate the extrapyramidal symptoms when co-administered with antipsychotics. Among these SSRIs, there are a few studies about paroxetine compared to fluoxetine or sertraline. In this study, we have intended to know the drug interaction of paroxetine and haloperidol when co-administered two drugs for the chronic schizophreinics by assessing the changes of positive, negative symptoms and extrapyramidal symptoms. For this purpose, we selected 29 subjects, the chronic schizophrenics with no physical problems. They were under maintenance therapy of haloperidol. They are randomly assigned to placebo group(n=12) and drug group(n=17) by using double blind method. And then, placebo or paroxetine 20mg were administered to the subjects of each groups during 8 week period. We have assessed their psychopathology and extrapyramidal symptoms using Positive and Negative Syndrome Scale(PANSS), Hamilton Rating Scale for Depression(HRSD), Simpson-Angus Scale at 0, 2, 4, 6, 8 weeks and serum haloperidol, reduced haloperidol levels at 0, 4, 8 weeks during the period. The results are analysed by using repeated measure MANOVA. 27 subjects have completed the study during 8 weeks, among the subjects, 1) PANSS, HRSD ; no significant difference between groups. 2) Simpson-Angus Scale ; no significant change according to the time and no significant difference between the groups(no group and time effect). 3) Haloperidol and reduced haloperidol level ; no siginificant change. When co-administered paroxetine and haloperidol, there are no significant changes of the psychopathology and no significant changes of the extrapyramidal symptoms. In this result, paroxetine seems to be not to affect the metabolism of haloperidol.

Keywords Paroxetine;Haloperidol;Drug interaction.