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Background: Understanding the impact of CYP2D6 metabolism on paroxetine, a widely used antidepressant, is essential for precision dosing., Methods: We conducted an 8-week, multi-center, single-drug, 2-week wash period prospective cohort study in 921 Chinese Han patients with depressive or anxiety disorders (ChiCTR2000038462). We performed CYP2D6 genotyping (single nucleotide variant and copy number variant) to derive the CYP2D6 activity score and evaluated paroxetine treatment outcomes including steady-state concentration, treatment efficacy, and adverse reaction. CYP2D6 metabolizer status was categorized into poor metabolizers (PMs), intermediate metabolizers (IMs), extensive metabolizers (EMs), and ultrarapid metabolizers (UMs). The influence of CYP2D6 metabolic phenotype on paroxetine treatment outcomes was examined using multiple regression analysis and cross-ethnic meta-analysis. The therapeutic reference range of paroxetine was estimated by receiver operating characteristic (ROC) analyses., Findings: After adjusting for demographic factors, the steady-state concentrations of paroxetine in PMs, IMs, and UMs were 2.50, 1.12, and 0.39 times that of EMs, with PM and UM effects being statistically significant (multiple linear regression, P = 0.03 and P = 0.04). Sex and ethnicity influenced the comparison between IMs and EMs. Moreover, poor efficacy of paroxetine was associated with UM, and a higher risk of developing adverse reactions was associated with lower CYP2D6 activity score. Lastly, cross-ethnic meta-analysis suggested dose adjustments for PMs, IMs, EMs, and UMs in the East Asian population to be 35%, 40%, 143%, and 241% of the manufacturer's recommended dose, and 62%, 68%, 131%, and 159% in the non-East Asian population., Interpretation: Our findings advocate for precision dosing based on the CYP2D6 metabolic phenotype, with sex and ethnicity being crucial considerations in this approach., Funding: National Natural Science Foundation of China; Academy of Medical Sciences Research Unit., Competing Interests: Declaration of interests The PMEDA consortium is funded by the Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences (2021-I2M-C&T-B-099) and “the Fundamental Research Funds for the Central Universities” (Peking University Medicine Fund for world's leading discipline or discipline cluster development, BMU2022DJXK007). WY, YL, Yu S, JG, ZK, and YZ disclose that there is a planned and pending patent related to a device for predicting the treatment outcome of paroxetine, which is relevant to the content of this manuscript. Other authors declare that they have no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Purpose: This study evaluated the effects of cytochrome P450 (CYP) 2D6 polymorphisms on the pharmacokinetics of controlled-release paroxetine in healthy Chinese subjects and used paroxetine as a tool drug to compare the performance of traditional phenotype and activity score systems., Methods: Pharmacokinetic data were evaluated in 24 subjects who received a single oral dose of 25 mg controlled-release paroxetine. Plasma paroxetine concentrations were measured by LC-MS/MS. CYP2D6 genotypes were tested by PCR and direct DNA sequencing. Subjects were classified by two systems of phenotype prediction. In the traditional phenotype system, subjects were classified as extensive metabolizers or intermediate metabolizers; in the activity score system, subjects were divided into four activity groups. Analysis of variance testing was applied to estimate the effects of CYP2D6 polymorphisms on the pharmacokinetics of paroxetine., Results: With the traditional phenotype system, significant differences were observed in the following pharmacokinetic parameters of paroxetine: t 1/2, C max, AUC0-t, AUC0-inf, Vz/F, and CL/F (all P < 0.05). The AUC or exposure of paroxetine was about 3.5-fold higher in the intermediate metabolizer group than in the extensive metabolizer group. With the activity score system, significant differences were observed in the t 1/2, C max, AUC0-t, AUC0-inf, Vz/F, and CL/F among the four different activity score groups (all P < 0.05). We found that the AUC of paroxetine decreased by around one half as the activity score increased by 0.5., Conclusion: The pharmacokinetics of controlled-release paroxetine after a single administration was affected by CYP2D6 polymorphisms. Both the traditional phenotype and the activity score systems performed well and distinguished subjects with different drug exposures. The activity score system provided a more detailed classification for the subjects.

To compare the efficacy and safety of augmenting paroxetine with risperidone, buspirone, valproate, trazodone, or thyroid hormone in patients with treatment-resistant depression (TRD), 225 patients with retrospectively and/or prospectively identified stage II TRD were randomly assigned to receive an 8-week treatment of paroxetine 20 mg/d augmented with risperidone 2 mg/d (n = 45), sodium valproate 600 mg/d (n = 39), buspirone 30 mg/d (n = 46), trazodone 100 mg/d (n = 47), or thyroid hormone 80 mg/d (n = 48). The primary outcome was the remission rate defined as the 17-item Hamilton Rating Scale for Depression score of 7 or less at the end of study. Secondary outcomes included remission rate based on the Self-rating Depression Scale score of 50 or less at the end of study, response rate based on 17-item Hamilton Rating Scale for Depression total score of 50% improvement or greater from baseline, and the change in scores of Clinical Global Impression-Improvement scale, the Short Form 36 Health Survey, and the Life Satisfaction Rating Scale. The remission rates were 26.7% for risperidone, 48.7% for valproate, 32.6% for buspirone, 42.6% for trazodone, and 37.5% for thyroid hormone. There was no statistical significance among treatment arms in remission rates, secondary outcome measures, and adverse events. Risperidone, valproate, buspirone, trazodone, or thyroid hormone augmentation to paroxetine 20 mg/d was effective and well tolerated in Chinese patients with TRD. Large-sample studies are warranted to support or refute these findings.