Correlation between myoclonus and the 3-glucuronide metabolites in patients treated with morphine or hydromorphone: A pilot study


  • Shawn McCann, MD
  • Tony L. Yaksh, PhD
  • Charles F. von Gunten, MD, PhD



morphine-3-glucuronide, hydromorphone-3-glucuronide, opioid neurotoxicity, myoclonus, morphine, hydromorphone


Background: The 3-glucuronide metabolites of morphine and hydromorphone have been implicated as a causative factor for patients exhibiting myoclonus.
Objective: The primary goal of this study was to determine plasma levels of morphine-3-glucuronide (M3G) or hydromorphone-3-glucuronide (H3G) in patients demonstrating myoclonus and identify any trends or associations between the two.
Setting: Patients were recruited from San Diego Hospice and the Institute for Palliative Medicine’s inpatient unit.
Design: A prospective convenience sample comprised of 17 subjects, 12 with myoclonus and 5 without myoclonus. Analysis included demographic, metabolic and clinical variables. Plasma was assayed via high performance liquid chromatography for morphine, M3G, and morphine-6-glucuronide or hydromorphone and hydromorphone-3-glucuronide.
Results: No trends or associations were identified between plasma levels of M3G or H3G and myoclonus. Ratio levels of 3-glucuronide metabolite to their corresponding parent opioid were dramatically lower than anticipated.
Conclusion: In this small pilot study, it appears that the serum levels of metabolites M3G and H3G do not correlate with myoclonus.

Author Biographies

Shawn McCann, MD

Research Fellow 2004-2005, The Institute for Palliative Medicine, San Diego Hospice, San Diego, California. E-mail:

Tony L. Yaksh, PhD

Professor of Anesthesiology and Pharmacology and Vice-Chairman for Research, Department of Anesthesiology, UCSD Co-director, Symptom Control Program, UCSD Moores Cancer Center, San Diego, California.

Charles F. von Gunten, MD, PhD

Provost, The Institute for Palliative Medicine, San Diego Hospice, San Diego, California; Medical Director, Doris A. Howell Service, UCSD Moores Cancer Center, San Diego, California.


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How to Cite

McCann, MD, S., Yaksh, PhD, T. L., & von Gunten, MD, PhD, C. F. (2018). Correlation between myoclonus and the 3-glucuronide metabolites in patients treated with morphine or hydromorphone: A pilot study. Journal of Opioid Management, 6(2), 87–94.