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Large-scale analysis demonstrates the influence of CYP2C19 genotype on specific SSRI side effects
Chris Eijsbouts1, Yunxuan Jiang2, James R Ashenhurst2
123andMe Research Institute, 2555 Park Boulevard, Palo Alto, CA, 94306, USA. chris.e@insitro.com.
The Pharmacogenomics Journal
|August 4, 2026
Summary
CYP2C19 genotype significantly impacts SSRI side effects and treatment discontinuation. Slower metabolizers experience more adverse events, suggesting pharmacogenetic-guided selection can improve depression treatment outcomes.
Area of Science:
- Pharmacogenetics
- Psychopharmacology
- Clinical Pharmacy
Background:
- Selective serotonin reuptake inhibitors (SSRIs) are first-line treatments for depression.
- Individual responses to SSRIs vary significantly.
- CYP2C19 genotype influences SSRI metabolism and potential efficacy.
Purpose of the Study:
- To investigate the association between CYP2C19 metabolizer status and SSRI response.
- To determine if genetic variations in CYP2C19 affect side effect profiles and treatment discontinuation rates.
- To evaluate the potential benefits of pharmacogenetic-guided SSRI selection.
Main Methods:
- Analysis of data from 114,627 research participants.
- Grading CYP2C19 metabolizer status from ultrarapid (0) to poor (4).
- Regression analysis of drug response outcomes against metabolizer grades.
Main Results:
- Slower CYP2C19 metabolizers taking escitalopram or citalopram reported significantly more side effects (OR=1.04-1.05 per grade).
- Slower metabolizers were more likely to discontinue SSRI treatment due to side effects (OR=1.05-1.07 per grade).
- Specific side effects like sleep and sexual problems (escitalopram) and tremor (sertraline) were more frequent in slower metabolizers.
Conclusions:
- CYP2C19 genotype is a significant determinant of SSRI-related side effects and treatment adherence.
- Pharmacogenetic testing can inform SSRI selection to minimize adverse events.
- Personalized pharmacogenetic-guided treatment strategies may enhance depression management and reduce discontinuations.
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