Integrating Pharmacogenomic Results and Drug-Induced Phenoconversion Concepts while Conducting a Medication Safety Review Process

Case Reports | 2 Minute Read

Pizzolato K, Thacker D, Del Toro-Pagán NM,  Hanna A, Turgeon J, Amin NS, Michaud V

Published 4/6/2022


Opioid appropriateness is primarily focused on insufficient pain control; however, opioid-related adverse drug events (ADE) have also been associated with a negative impact on disability, mood, and quality of life. As progress is made toward determining more appropriate parameters for opioid prescribing, clinicians are beginning to rely on pharmacogenomics (PGx). PGx results can provide valuable patient-specific information about risk for opioid-related ADEs and/or pharmacotherapy failure. The clinical utility of PGx has been associated with limitations; however, considering drug-induced phenoconversion can be a strategy to address limitations in patients with complex drug regimens. This case highlights the importance of considering drug-induced phenoconversion when implementing PGx into clinical practice. This case describes a wheelchair-bound patient who experienced intolerable drowsiness due to oxycodone which was unsuccessful in relieving trigeminal neuralgia-related pain. A clinical pharmacist performed a PGx-informed medication safety review and identified drug interactions causing competitive inhibition of CYP3A4 and drug-drug-gene interactions and drug-induced phenoconversion for CYP2D6 – all of which affected oxycodone metabolism into oxymorphone. This resulted in an increased risk for oxycodone-related ADEs and decreased efficacy. The pharmacist recommended oxycodone discontinuation, optimization of gabapentin, awareness for alternative therapy based on HLA-A PGx results, and patient counseling. Pursuant to therapy changes, the patient experienced better pain control and less drowsiness, which improved her quality of life. This report demonstrates how a PGx-informed medication safety review that assessed drug-drug and drug-drug-gene interactions resulted in better pain management, elimination of opioid-related ADEs, and improved quality of life.

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