Purpose: Methadone, an opioid traditionally associated with the management of opioid addictive disorders, has been prescribed increasingly as an analgesic for the management of various chronic pain conditions. Despite the increasing popularity of methadone, most anesthesiologists are not familiar with its complex pharmacology. The purpose of this article is to review the pharmacology of methadone and to suggest a management algorithm for the perioperative care of methadone patients.
Source: A Medline search was performed to obtain the published literature on the pharmacology of methadone and its use perioperatively.
Principal findings: The complexity of methadone's pharmacology is characterized by a high inter-individual variability, a potential for interaction with other medications, and a long elimination half-life. The postoperative management of methadone patients may be difficult as they are often 'opioid-tolerant' but may be 'pain-intolerant'. For those patients who are taking part in methadone-maintenance programs, there is a potential for the problematic use of opioids or other substances. The management plan for patients taking methadone may differ depending on the type of surgery and the associated perioperative differences in fasting status and gastrointestinal function. In consideration of all the factors listed above, a management algorithm is outlined for the perioperative care of methadone patients.
Conclusion: Methadone is an opioid with complex properties, and a patient that is taking methadone can represent a unique challenge to the anesthesiologist. A good understanding of the pharmacology of methadone and of the type of patients on this medication will help to improve their perioperative care.