Considerations for the Utility of the CPIC Guideline for CYP2D6 Genotype and Codeine Therapy.

Abstract

To the Editor: We appreciate the recent Perspective from Nicholson and Formea (1) because it allows us to clarify the role of Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for clinicians. CPIC publishes genotype-based drug therapy guidelines to help clinicians understand how genetic test results could be used to optimize drug therapy. The underlying assumption for CPIC guidelines is that clinical high-throughput and preemptive genotyping will become common practice and clinicians will increasingly have patients' genotypes, such as a cytochrome P450, family 2, subfamily D, polypeptide 6 ( CYP2D6 ) genotype test result, available before a prescription is written (2, 3). Therefore, CPIC guidelines provide guidance on how to interpret available genetic test results to improve drug therapy. For example, patients carrying 2 nonfunctional alleles that give rise to CYP2D6 poor metabolizer status derive little or no pain relief from codeine and tramadol. Thus the CPIC guideline recommends avoiding their use in these patients due to lack of efficacy and to use alternative pain medications. The guideline discusses that although alternatives might include hydrocodone or oxycodone, both have limitations. The guideline states that “there is insufficient evidence to conclude whether poor …