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

Abstract

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.