Optimizing the individual dosing of paroxetine in major depressive disorder with therapeutic drug monitoring.

Abstract

Previous studies have examined the correlation between paroxetine concentrations and therapeutic efficacy in patients diagnosed with major depressive disorder (MDD), but findings have been contradictory. This study aimed to investigate the relationships among plasma concentrations, severity of symptoms, and adverse drug reactions (ADRs) to optimize individual dosing. Eighty-seven MDD patients, after completing treatment with paroxetine, were divided into low-concentration (LC, n = 38), medium-concentration (MC, n = 27), and high-concentration (HC, n = 22) groups, based on cutoff value concentrations with the 50% response rate and the laboratory alert level from the 2017 consensus guidelines for therapeutic drug monitoring in neuropsychopharmacology. The severity of depression and anxiety was evaluated using a 17-item Hamilton Depression Scale (HAMD-17) and Hamilton Anxiety Scale (HAMA), respectively. Dosage, plasma concentrations, scale scores, and ADRs were recorded across the three groups at different treatment stages to define the therapeutic reference range. The 4-week plasma concentration of paroxetine (65.00 ng/mL) could predict the clinical response in MDD patients at 8 weeks. Symptom relief in patients with 4-week paroxetine concentrations ranging from 65.00 to 120.00 ng/mL at 8 weeks was greater than in those with concentrations below 65.00 ng/mL, with no significant difference observed above this range. In addition, more cases of liver injury and weight gain were observed in patients with high paroxetine concentrations. Our results support that early paroxetine concentration may predict clinical efficacy and the incidence of ADRs, thus improving individual dosing regimens for MDD patients.