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Updated: May 14, 2026

Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Intermittent subcutaneous morphine regimen for postoperative pain management following abdominal hysterectomy
Danuta Szkutnik-Fiedler1, Hanna Billert, Edmund Grzeskowiak
1Department of Clinical Pharmacy and Biopharmacy, Poznań University of Medical Sciences, Poznań, Poland.
Objectives:
Systemic β-endorphin, an endogenous opioid and stress hormone, has been demonstrated to correlate with the postoperative pain intensity, however its putative role as a postoperative pain biomarker has not been cleared.
Methods:
Thirty patients scheduled for elective hysterectomy were included into the study. Postoperative pain was assessed by a numeric rating scale from 0 to 10. Plasma morphine concentrations were determined using high performance liquid chromatography with UV detection. Plasma β-endorphin concentrations were measured by a radioimmunoassay.
Results:
Administration of morphine in intravenous infusion turned out to be a markedly better method of morphine administration up to 4th hour postoperatively regarding both drug concentration and pain rating. A significant correlation between systemic β-endorphin concentration and pain rating at the 4th postoperative hour was found. No association between morphine and β-endorphin concentrations was detected.
Conclusion:
Systemic β-endorphin is not an appropriate pain marker in postoperative gynaecologic patients.
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