The CYP2D6 poor metabolizer status indicates that this patient will have elevated plasma levels of medications primarily metabolized by CYP2D6

This may explain her history of SSRI intolerance due to supratherapeutic drug exposure at standard doses. Pharmacogenomic results should be integrated with clinical history and used as one component of an individualized treatment plan rather than as the sole determinant of medication selection. For this patient, medications with significant CYP2D6 metabolism, such as paroxetine and fluoxetine, should be used cautiously at reduced doses or avoided, while medications with alternative metabolic pathways or less CYP2D6 dependence may be better tolerated. The PMHNP should also consider that her CYP2C19 rapid metabolizer status may result in lower-than-expected plasma levels for medications primarily cleared through this pathway, potentially requiring higher doses for therapeutic effect.

The CYP2D6 poor metabolizer status means the patient metabolizes CYP2D6 substrates too quickly

Resulting in subtherapeutic drug levels that explain her inadequate response and early side effects due to ineffective serotonergic modulation. The appropriate treatment plan is to select a medication with high CYP2D6 dependence and prescribe it at higher-than-standard doses to compensate for the accelerated metabolism. Paroxetine at 40 mg daily would be the optimal choice because it is the most potent SSRI and its high CYP2D6 dependence allows for predictable dose-response adjustments based on metabolizer status. The CYP2C19 rapid metabolizer status is clinically insignificant because this enzyme plays a minor role in antidepressant metabolism and does not meaningfully affect drug levels or clinical outcomes. This answer fundamentally misinterprets pharmacogenomic terminology.

Pharmacogenomic testing definitively identifies which medications will be effective and which will cause side effects for this specific patient

The results should replace clinical judgment in guiding medication selection going forward. The PMHNP should select only medications categorized as having no gene-drug interactions on the pharmacogenomic report, as any medication with a flagged interaction will inevitably cause adverse effects or treatment failure in this patient. The CYP2D6 poor metabolizer finding means all antidepressants in any class will require dose reduction because CYP2D6 is the primary metabolic pathway for the entire antidepressant pharmacopeia. This information should be documented as a permanent contraindication to standard-dose antidepressant therapy in the patient's medical record.

Given the pharmacogenomic findings, the PMHNP should plan to switch the patient to a non-pharmacological treatment modality exclusively

Because the combination of CYP2D6 poor metabolizer and CYP2C19 rapid metabolizer status creates a metabolic profile that is fundamentally incompatible with safe antidepressant pharmacotherapy. These combined findings indicate that no antidepressant can achieve stable therapeutic levels because the opposing metabolic tendencies will produce unpredictable plasma concentration fluctuations for any serotonergic or noradrenergic medication. Referral for psychotherapy as monotherapy, specifically cognitive-behavioral therapy or interpersonal therapy, should be the primary treatment plan until future pharmacogenomic advances offer more targeted medication options.