Review of opioid conversion recommendations from select clinical practice guidelines: all are not equal

Clinicians often rely on published opioid analgesic conversion tables to convert between opioids or administration routes for patients with chronic pain. Sources of conversion tables include Full Prescribing Information (FPI) for a specific product, or clinical guidelines promulgated by learned societies or government entities. Concerns identified with conversion estimates include overestimating “equianalgesic” doses and failure to consider incomplete cross-tolerance, the likely pain trajectory, comorbidities, concomitant medicines, and inter-patient variability. Most conversion estimates are based on single-dose, relative potency studies, not conversion in ongoing care. There are conflicting recommendations in the literature and no uniformly-accepted conversion ratios. To raise awareness regarding the variability in currently-available oral opioid conversions, a review was conducted of selected guidelines issued by North American professional societies or federal and State government entities, and the source data cited by the guidelines. Our analysis focused on the suggested conversion ratios for oral opioids, the source data for the opioid conversion ratios, recommended dose reductions to account for incomplete cross-tolerance, considerations for supplemental analgesics during conversion, and patient factors when selecting an initial opioid conversion dose. This analysis found that variability exists in the recommendations for conversion ratios, incomplete cross-tolerance, and supplemental analgesia. In addition, the sources for the opioid conversion ratios in most guidelines are not well-controlled, multiple-dose trials in chronic pain patients. Therefore, it is imperative that practitioners are aware of these clinically-meaningful limitations and consider the reliability and applicability of these conversion ratios to the setting of chronic opioid administration. Likewise, legislators and regulators contemplating the use of conversion ratios in implementing pain policies should understand the unresolved variability and lack of bi-directionality in conversion tables. Efforts to determine scientifically-sound conversion recommendations should continue and, once determined, they should be widely available (eg, FPIs, websites). The authors are full-time employees of Purdue Pharma L.P.