PHARMACOLOGICAL EFFECTS OF PAROXETINE ON HEMODYNAMIC CHANGES MEASURED BY NEAR INFRARED SPECTROSCOPY IN PATIENTS WITH OBSESSIVE-COMPULSIVE DISORDER
Authors: Mukai *Keiichiro , Hosoi Yukihiko , Ogino Shun , Maebayashi Kensei , Hayashida Kazuhisa , Matsunaga Hisato 
Published: February 2025

Abstract

Background
Several studies using near-infrared spectroscopy (NIRS) have commonly indicated that hemodynamic changes in patients with Obsessive-Compulsive Disorder (OCD) are lower than healthy control. However, the effect of pharmacotherapy on hemodynamic changes in OCD patients has not been verified.

Aims
In this study, we compared the pharmacological effects of paroxetine (PXT) on hemodynamic changes measured by NIRS among OCD patients with/without medication and healthy controls.

Methods
Forty patients who met the diagnostic criteria for OCD in DSM-5 were included in the study; 18 were assigned to the PXT group and the others (20 patients) were in the group without any medication. Age- and gender-matched healthy controls were also recruited. The Yale-Brown Obsessive- Compulsive Scale (YBOCS) was used to assess severity, and various clinical rating scales were performed. Hemodynamic changes in the frontal lobe were measured by NIRS (spectratech OEG-16) during 30- and 60-second Verbal fluency tasks. Four indices were used to evaluate changes in hemodynamic changes: initial activation of [oxy-Hb], integrated value, center of gravity value, and β value from generalized linear model analysis. Subjects were informed of the details of the study and their written consent was obtained. The study was approved by the Ethics Committee of Hyogo Medical University.

Results
No significant differences were found in task scores among the groups. Compared to the control group, both OCD groups had lower integral values for the 30-second task (PXT group ch2-13, 15; drug- free group 3-6, 8, 9, 13, 15) without any significant differences between the OCD groups. In the correlation analysis, a significantly negative correlation was detected between the dose (mg) of PXT and the integral value (ch3, p &lt;0.05), and between the YBOCS score and the initial activation value (ch4, p &lt;0.01) in the PXT group.

Discussion
The result of this study which exhibited lower hemodynamic changes in patients with OCD, is consistent with previous studies. Our results suggested that lower hemodynamic changes are consistently observed in OCD patients, regardless of the presence or absence of medication including PXT. However, a significantly negative correlation between the dose of PXT and hemodynamic changes was detected, which is consistent with the previous study in patients with depression. PXT is characterized by a nonlinear increase in blood concentration dependent on the doses, not presenting a correlation between the doses and blood concentration. Thus, the relationship between the doses and cerebral blood flow change may be modified by the involvement of complex factors such as pharmacokinetics and functional connectivity between the amygdala and frontal lobe. Therefore, it should be cautious in the discussion of the results.

Conclusion
The results of this study suggest the possibility that standardized pharmacotherapy such as PXT may affect hemodynamic changes in patients with OCD, which may be related to the pharmacological effectiveness of OCD.