Title: Fast Fact and Concept #86: Methadone: Starting dose information
Author(s): Charles F. von Gunten, MD
Methadone is an effective opioid analgesic for severe pain. Because of low cost (a month's supply may be US$ 5-10) and apparent efficacy in complex pain syndromes, it is increasingly used as a first-line opioid. It is, in effect, a combination drug - part opioid and part NMDA receptor antagonist. Methods of dose conversion to methadone from other opioid analgesics that account for this dual action were discussed in Fast Fact #75: Methadone for Pain. This Fast Fact will describe strategies for beginning methadone when the patient has not been taking a strong opioid. Note: due to its complex pharmacology, physicians unfamiliar with methadone are advised to seek consultation prior to initiating therapy.
Methadone is lipophilic, thus it takes time to develop tissue stores that maintain serum levels. Note: There is enormous interindividual variation. After a single dose there is a short distribution phase (associated with acute pain relief) with half-life of 2-3 hours and a slow elimination phase (half-life 15-60 hours). Dosing must account for the accumulation of drug over days. It is this accumulation that accounts for most therapeutic misadventures. Liver metabolites are inactive; therefore no dose reduction is required with renal failure. After steady-state is reached, about two-thirds of patients will get adequate pain relief maintained with twice a day (bid) dosing. Note: a number of drugs will alter methadone metabolism, there needs to be close follow-up and attention to the addition or subtraction of interacting medications.
There are several approaches to starting methadone for the treatment of pain. All take into account the long-half life of the drug that leads to drug accumulation over days. The following discussion presents approaches based on the literature and the authors? clinical experiences.
Loading Dose Approach
Conversion to Methadone From Another Strong Opioid
Calculate Total Methadone Dose (for conversion information, see FF# 75). Convert step wise in order to detect if the patient demonstrates a therapeutic response to a much lower dose of methadone that you had expected.
Bruera E, Sweeney. Methadone use in cancer patients with pain: a review. J Pall Med 2002; 5:127-138.
Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing. Fast Facts and Concepts #86 . Methadone: Starting dose information. Von Gunten, CF., March 2003. End-of-Life Physician Education Resource Center www.eperc.mcw.edu.
Disclaimer: Fast Facts provide educational information, this information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Fact information cites the use of a product in dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.
Creation Date: 3/2003
Purpose: Instructional Aid, Self-Study Guide, Teaching
|Training: Fellows, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice|
|Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery|
ACGME Competencies: Medical Knowledge, Patient Care
Keyword(s): Addiction, Chronic non-malignant pain, Controlled substance regulations, Pain, Pain assessment, Pain treatment
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