Equianalgesic dose guidelines for long-term opioid use: Theoretical and practical considerations

Abstract

From the Department of Anesthesiology and Pain Services, University of Washington Medical Center, Seattle, WA. Address reprint requests to Karen J. Souter, MB, BS, MSc, FRCA, Department of Anesthesiology and Pain Services, University of Washington Medical Center, 1959 NE Pacific Street, Box 356540, Seattle, WA 98195-6540. © 2004 Elsevier Inc. All rights reserved. 1547-9951/04/2304-0000$30.00/0 Patients receiving long-term opioids for the management of chronic cancer-related and noncancer pain may develop tolerance and/or adverse effects to these drugs requiring conversion to a different opioid analgesic. There are a number of theoretical reasons for the development of tolerance to opioids. Tolerance to various opioid analgesics may develop at different rates in the same patient. Between patients, tolerance to the same opioid can develop at variable rates. Opioid conversion tables in current use were developed in general from single-dose studies in opioid-naive patients and therefore may not be accurate or safe to use when changing from one opioid to another in opioid-tolerant patients. Recent publications provide some guidelines for opioid conversions in this patient population. Opioid therapy is well established in the management of a variety of painful conditions. Short-term control of pain related to acute medical conditions and surgical procedures commonly involves opioid therapy and is generally well accepted. Long-term use of opioids for chronic pain conditions is also becoming increasingly accepted. In the management of cancer-related pain, most clinicians agree that opioids play an essential role, and there is now increasing evidence for the efficacy of opioids in the management of chronic nonmalignant pain. The adequate management and persistent undertreatment of pain, however, remains a major public health concern and various professional societies, governmental, and regulatory agencies have developed standards and guidelines for long-term opioid prescription. These guidelines usually include recommendations for careful, comprehensive assessment of the pain complaint and close monitoring of the response to opioid therapy.