Abstract
The radiolabelled opioid receptor binding affinities of morphine and its active metabolite morphine 6-glucuronide at the total mu, mu 1, mu 2 and delta receptors were determined. Morphine 6-glucuronide was found to have a 4-fold lower affinity for the mu 2 receptor (IC50 17 nM and 82 nM for morphine and morphine 6-glucuronide respectively, P = 0.01), the receptor postulated to be responsible for mediating the respiratory depression and gastrointestinal effects after morphine. This provides a possible explanation for the reduced respiratory depression and vomiting seen following morphine 6-glucuronide in man. A similar reduction in affinity of morphine 6-glucuronide was seen at the total mu receptor whilst there was no significant difference seen at the mu 1 or delta receptor. Hence the increased analgesic potency of morphine 6-glucuronide over morphine remains unexplained.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 24 print issues and online access
$259.00 per year
only $10.79 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Hucks, D., Thompson, P., McLoughlin, L. et al. Explanation at the opioid receptor level for differing toxicity of morphine and morphine 6-glucuronide. Br J Cancer 65, 122–126 (1992). https://doi.org/10.1038/bjc.1992.23
Issue Date:
DOI: https://doi.org/10.1038/bjc.1992.23
This article is cited by
-
Heroin and its metabolites: relevance to heroin use disorder
Translational Psychiatry (2023)
-
Role of active metabolites in the use of opioids
European Journal of Clinical Pharmacology (2009)
-
Morphine‐6β‐glucuronide has a higher efficacy than morphine as a mu‐opioid receptor agonist in the rat locus coeruleus
British Journal of Pharmacology (2000)
-
Pharmacology of morphine metabolites
Current Review of Pain (1997)