Precision medicine in psychiatry: Case series on pharmacogenomic solutions for treatment-resistant depression

Treatment-resistant depression (TRD) is a persistent challenge in psychiatry, affecting approximately 30% of patients with major depressive disorder. Defined by the failure to achieve remission after two adequate trials of antidepressants at therapeutic doses, TRD significantly impairs quality of life, heightens suicide risk, and increases health care utilization and economic burden. Current treatment paradigms rely heavily on trial and error, often leading to delayed symptom relief and exposure to unnecessary side effects. This underscores the urgent need for personalized approaches to care. Pharmacogenomic testing has emerged as a transformative tool in addressing the complexities of TRD. By analyzing genetic polymorphisms, such as those in cytochrome P450 enzymes, serotonin transporter, and methylenetetrahydrofolate reductase, pharmacogenomics offers insights into drug metabolism, receptor sensitivity, and neurotransmitter synthesis. This precision approach enables clinicians to optimize antidepressant selection, dosing, and augmentation strategies, minimizing adverse effects and enhancing therapeutic outcomes. This case series highlights the clinical utility of pharmacogenomic testing in managing TRD. Three diverse cases illustrate how genetic insights guided tailored interventions, leading to significant improvements in depressive symptoms, enhanced adherence, and overall patient satisfaction. The findings underscore pharmacogenomics' potential to shift psychiatry from trial and error to precision medicine, improving outcomes for patients with complex treatment histories. Despite challenges, such as cost, accessibility, and the need for clinician training, integrating pharmacogenomics into routine practice represents a promising avenue for advancing the management of TRD and enhancing the quality of psychiatric care.