Highlights
The CYP2D6-guided opioid management trial represents a significant effort to integrate pharmacogenomics into acute surgical care. The key findings include:
- Genotype-guided prescribing significantly increased the rate of concordance between a patient’s metabolizer phenotype and the prescribed opioid (64% vs 27%).
- Despite improved prescribing alignment, there was no statistically significant difference in the primary outcome, the 10-day Silverman integrated analgesic assessment (SIA) score.
- Secondary outcomes, including average pain intensity and total opioid consumption (MME/d), remained similar between the genotype-guided and control groups.
- The results suggest that in the contemporary era of multimodal analgesia, the clinical impact of CYP2D6-guided opioid selection may be minimal.
Background: The Promise and Pitfalls of Pharmacogenomics in Pain
Cytochrome P450 2D6 (CYP2D6) is a highly polymorphic enzyme responsible for the metabolism of approximately 25% of clinically used drugs, including common opioids like codeine, tramadol, and hydrocodone. These specific opioids are prodrugs that require CYP2D6-mediated conversion into their more potent active metabolites—morphine, O-desmethyltramadol, and hydromorphone, respectively—to exert significant analgesic effects.
Individuals categorized as poor metabolizers (PMs) or intermediate metabolizers (IMs) possess genetic variations that result in low or absent enzyme activity. For these patients, standard doses of codeine or tramadol often fail to provide adequate analgesia because the active metabolites never reach therapeutic concentrations. Conversely, ultra-rapid metabolizers (UMs) are at risk of toxicity due to rapid overproduction of these metabolites. While professional guidelines, such as those from the Clinical Pharmacogenetics Implementation Consortium (CPIC), recommend avoiding these prodrugs in PMs and IMs, high-level evidence from randomized clinical trials (RCTs) has been lacking to prove that such interventions improve patient-centered outcomes in the acute postoperative setting.
Study Design and Methodology
The IGNITE Pragmatic Trials Network conducted this open-label RCT across eight US health systems between March 2021 and September 2023. The study enrolled 1,602 participants undergoing major surgeries anticipated to require at least 7 to 10 days of postoperative pain management, predominantly total knee and hip arthroplasties.
Participants were randomized into two arms: the CYP2D6-guided arm and the control (usual care) arm. In the guided arm, participants underwent genotyping before surgery. If they were identified as PMs or IMs (the actionable phenotype), clinicians were advised to avoid tramadol, hydrocodone, and codeine, opting instead for non-CYP2D6-dependent opioids or non-opioid alternatives. The control arm followed standard institutional protocols without genotype information.
The primary endpoint was the 10-day Silverman integrated analgesic assessment (SIA) score. This composite measure ranks participants based on both their average pain intensity (on a 10-point scale) and their total opioid consumption (measured in morphine milligram equivalents, or MMEs). This dual-measure approach is designed to capture the trade-off between pain relief and drug exposure.
Key Results: Prescribing Shifts Without Clinical Gain
The analytical population focused on the 351 participants who possessed an actionable phenotype (PM or IM) and completed their surgery. The demographic profile was 68% female with a mean age of 62 years.
Prescribing Concordance
The intervention successfully influenced clinician behavior. Concordance between the patient’s genotype and the prescribed opioid was 64% in the guided arm compared to only 27% in the control arm (difference, 37 percentage points; P < .001). This indicates that the pharmacogenomic data were actively utilized by the surgical teams to modify therapy.
Primary and Secondary Outcomes
Despite the change in prescribing, clinical outcomes did not diverge. At the 10-day mark, the mean SIA score was 1.4 in the guided arm and -1.4 in the control arm (difference, 2.8; 95% CI, -18.3 to 23.8; P = .80). There were no significant differences in the individual components of the SIA score:
- Mean numeric pain intensity: 5.2 (guided) vs 5.1 (control).
- Mean daily opioid use: 13.7 MME/d (guided) vs 13.2 MME/d (control).
Furthermore, other secondary endpoints, including physical function and opioid-related side effects, showed no significant differences between the two study groups.
Expert Commentary: Why the Multi-Modal Context Matters
The failure of the intervention to improve outcomes, despite successful implementation of prescribing changes, raises critical questions about the role of precision medicine in modern surgery. A primary explanation offered by the investigators and outside experts is the prevalence of multimodal analgesia. Contemporary postoperative protocols rely heavily on non-opioid medications—such as NSAIDs, acetaminophen, and gabapentinoids—alongside regional anesthesia and nerve blocks.
In this environment, opioids often serve as “rescue” medications rather than the primary driver of pain control. When the overall reliance on opioids is low, the incremental benefit of selecting a genetically “optimal” opioid may be too small to detect. Additionally, the study population was heavily weighted toward orthopedic procedures (78% arthroplasties), which are standardly managed with robust multimodal pathways. It remains possible that in surgical settings where multimodal options are limited, or in chronic pain management, the impact of CYP2D6 testing could be more pronounced.
Limitations and Generalizability
Several factors may limit the generalizability of these findings. First, the trial was open-label, which could introduce bias, though the lack of difference in outcomes suggests that any bias did not favor the intervention. Second, the study did not specifically focus on ultra-rapid metabolizers (UMs), who are at the highest risk for opioid toxicity, because they represent a much smaller percentage of the population. Finally, the 10-day window primarily captures acute recovery; long-term impacts on opioid cessation or chronic pain transition were not the focus of this analysis.
Conclusion: Reassessing the Utility of CYP2D6 Testing
The IGNITE trial provides high-quality evidence that routine CYP2D6 genotyping for the selection of postoperative opioids does not improve pain control or reduce opioid use in patients undergoing major surgery within a modern healthcare framework. While pharmacogenomics remains a powerful tool for certain medications (e.g., clopidogrel or antidepressants), its application in acute postoperative pain appears limited when robust multimodal analgesic protocols are already in place.
Clinicians should continue to prioritize evidence-based multimodal strategies, reserving pharmacogenomic testing for cases where therapy fails or when specific drug-drug interactions and genetic factors significantly complicate the clinical picture. The data do not support the broad, routine implementation of CYP2D6-guided opioid therapy in the current surgical landscape.
Funding and clinicaltrials.gov
This study was supported by the National Human Genome Research Institute (NHGRI) and the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health. Trial registration: ClinicalTrials.gov Identifier: NCT05966129.
References
- Cavallari LH, et al. CYP2D6-Guided Opioid Management and Postoperative Pain Control: A Randomized Clinical Trial. JAMA Netw Open. 2026;9(2):e2558299. doi:10.1001/jamanetworkopen.2025.58299.
- Crews KR, et al. Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for cytochrome P450 2D6 genotype and codeine therapy: 2014 update. Clin Pharmacol Ther. 2014;95(4):376-382.
- Chidambaran V, et al. Pharmacogenetics of postoperative opioid management: A review of the current evidence and future directions. J Clin Anesth. 2017;39:46-56.
