Cited by 73Opioid Use Disorder TreatmentNeuropeptides and Animal PhysiologyNeurotransmitter Receptor Influence on Behavior

Using [11C]Diprenorphine to Image Opioid Receptor Occupancy by Methadone in Opioid Addiction: Clinical and Preclinical Studies

Melichar, Jan K., Hume, Susan P., Williams, Tim M., Daglish, Mark R.C., Taylor, Lindsay G., Ahmad, Rabia, Malizia, Andrea L., Brooks, David J. +3 more·2005·The Journal of Pharmacology and Experimental Therapeutics

Abstract

Substitute methadone prescribing is one of the main modes of treatment for opioid dependence with established evidence for improved health and social outcomes. However, the pharmacology underpinning the effects of methadone is little studied despite controversies about dosing in relation to outcome. We therefore examined the relationship between methadone dose and occupation of opioid receptors in brain using the positron emission tomography (PET) radioligand [(11)C]diprenorphine in humans and rats. Eight opioid-dependent subjects stable on their substitute methadone (18-90 mg daily) had an [(11)C]diprenorphine PET scan at predicted peak plasma levels of methadone. These were compared with eight healthy controls. No difference in [(11)C]diprenorphine binding was found between the groups, with no relationship between methadone dose and occupancy. Adult male Sprague-Dawley rats that had been given an acute i.v. injection of methadone hydrochloride (0.35, 0.5, 0.7, or 1.0 mg kg(-1)) before [(11)C]diprenorphine showed a dose-dependent increase in biodistribution but no reduction in [(11)C]diprenorphine binding. We suggest that the lack of a dose-dependent relationship between methadone dose, either given chronically in human or acutely in rat, and occupancy of opioid receptor measured with [(11)C]diprenorphine PET is related to efficacy of this opioid agonist at very low levels of opioid receptor occupancy. This has implications for understanding the actions of methadone in comparison with other opioid drugs such as partial agonists and antagonists.

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Crossref · 10.1124/jpet.104.072686

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  • Imaging of the relationship between methadone and opioid receptors has been difficult, with two studies finding no relationship between dose and occupancy of opioid receptors.

    “Unfortunately, imaging of the relationship between methadone and opioid receptors has been difficult with two studies finding no relationship between dose and occupancy of opioid receptors.38,39”
  • The lack of relationship between methadone dose and opioid receptor occupancy has been attributed to either the insensitivity of the radiotracers used, or to their inability to label receptors internalised by methadone agonism.

    “This has been attributed to either the insensitivity of the radiotracers used, or to their inability to label receptors internalised by methadone agonism. 38”

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Authors
Melichar, J. K., Hume, S. P., Williams, T. M., Daglish, M. R. C., Taylor, L. G., Ahmad, R., Malizia, A. L., Brooks, D. J., Myles, J. S., Lingford-Hughes, A., & Nutt, D. J.
Affiliations
University of Bristol (GB)
Venue
The Journal of Pharmacology and Experimental Therapeutics
Publisher
Elsevier BV
Published
2005-01
Volume
312
Issue
1
Pages
309-315
ISSN
0022-3565 (ISSN-L)
OpenAlex
W2143095325
Cited by
71
References
38
Citations by year
2026: 2 · 2025: 3 · 2024: 1 · 2023: 3 · 2022: 1 · 2021: 1 · 2020: 6 · 2019: 3 · 2018: 3 · 2017: 1 · 2016: 2 · 2014: 4 · 2013: 8 · 2012: 4
FWCI
5.85
Type
journal article
Language
en
Open access
closed
Locations
  • Journal of Pharmacology and Experimental Therapeutics (publishedVersion)
  • PubMed (publishedVersion)
  • Explore Bristol Research (publishedVersion)
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Opioid Use Disorder Treatment
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuropeptides and Animal Physiology
  • Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neurotransmitter Receptor Influence on Behavior
Keywords
methadone, opioid use disorder, methadone dose, PET radiotracer, opioid agonists, opioid receptor binding
MeSH terms
Adult, Animals, Carbon Radioisotopes, Diprenorphine, Humans, Male, Methadone, Middle Aged, Opioid-Related Disorders, Receptors, Opioid, Time Factors, Behavior, Addictive, Rats, Sprague-Dawley, Rats

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