Morphine-3-glucuronide: evidence to support its putative role in the development of tolerance to the antinociceptive effects of morphine in the rat

Smith G.D. and Smith M.T. (1995) Morphine-3-glucuronide: evidence to support its putative role in the development of tolerance to the antinociceptive effects of morphine in the rat. Pain, 62 1: 51-60. doi:10.1016/0304-3959(94)00228-7


Author Smith G.D.
Smith M.T.
Title Morphine-3-glucuronide: evidence to support its putative role in the development of tolerance to the antinociceptive effects of morphine in the rat
Journal name Pain   Check publisher's open access policy
ISSN 0304-3959
Publication date 1995
Sub-type Article (original research)
DOI 10.1016/0304-3959(94)00228-7
Volume 62
Issue 1
Start page 51
End page 60
Total pages 10
Language eng
Subject 2703 Anesthesiology and Pain Medicine
2728 Clinical Neurology
2808 Neurology
3004 Pharmacology
2738 Psychiatry and Mental health
2800 Neuroscience
3203 Clinical Psychology
Abstract Antinociceptive tolerance to morphine (MOR) was induced in groups of Sprague-Dawley rats receiving continuous intravenous infusions of morphine sulphate administered by 3 different MOR dosing regimes. At appropriate intervals throughout each infusion period, antinociceptive testing was performed using the tail-flick latency test and blood samples were collected. Groups of saline (SAL)-infused control rats also underwent antinociceptive testing and blood sample collection. Complete antinociceptive tolerance developed during each MOR infusion period and was characterized by a marked decline in the degree of antinociception from values greater than 90% of the maximum possible effect (%MPE) to pre-dosing baseline values. By contrast, %MPE values in SAL-infused control animals and in sham-operated rats were not significantly different from pre-dosing values throughout the infusion period, indicating that the experimental procedures themselves did not contribute to the development of antinociceptive tolerance to MOR. In addition, the rate of MOR tolerance development was inversely proportional to the MOR infusion rate. A very significant inverse relationship was observed between the mean degree of antinociception (%MPE) and the mean plasma molar concentration ratio, [morphine-3-glucuronide]/[MOR], for each of the 3 MOR dosing regimes and for the cumulated data. This relationship showed that near-maximum antinociception was attainable at ratio values less than approximately 0.50, whilst at ratio values above approximately 1.5, little or no antinociception was observed. Although %MPE was highly inversely correlated with the mean plasma morphine-3-glucuronide (M3G) concentrations for rats receiving regimes A and B, this was not the case for rats receiving regime C where antinociceptive tolerance was partially reversed by an increase in the morphine infusion rate part-way through the infusion period. In addition, a poor relationship was observed between %MPE and the mean plasma MOR concentration, possibly due to the confounding presence of M3G in all samples. Thus, we may conclude from this study in Sprague-Dawley rats that irrespective of the rate of antinociceptive tolerance development, the level of antinociception achievable appears to be highly inversely correlated with the mean [M3G]/[MOR] plasma molar concentration ratio and poorly correlated with the plasma MOR concentration, consistent with the notion that it is perhaps the balance between the excitatory effects of M3G and the inhibitory effects of MOR at the functional level which is the important determinant. Further research is required in carefully conducted studies in cancer patients to evaluate the possible contribution of the MOR metabolites. M3G and morphine-6-glucuronide (MbG), to increasing dosing requirements of MOR. Other factors such as disease progression and increasing psychological distress must also be borne in mind, as these will have a major influence on increasing dosing requirements of MOR in cancer patients (Portenoy 1994).
Keyword Antinociceptive Tolerance
Morphine
Morphine-3-glucuronide
Pain
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
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Citation counts: TR Web of Science Citation Count  Cited 51 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 59 times in Scopus Article | Citations
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