Decisions about the most appropriate treatment approach need to take into account features of the physical examination (the frequency and intensity of symptoms, hydration status, and estimated prognosis) and information from the medical record (temporal pattern of opioid use and dose escalation, other medications, and the presence of electrolyte abnormalities and major organ dysfunction).
Whenever medically appropriate, easily treatable causes or exacerbating factors should be corrected (e.g. correct hypomagnesemia).
Options for management of opioid induced neurotoxicity
Mild myoclonus may trouble family members more than the patient. If the patient is satisfied with current therapy, explaining the cause/progression of symptoms may be all that is necessary.
Opioid dose reduction
Myoclonus may resolve over a few days with a decrease in opioid dose. Note
: do not reduce the opioid dosage solely to control myoclonus at the expense of good pain control.
Rotate to a dissimilar opioid
Rotating to a lower dosage of a structurally dissimilar opioid will often reduce myoclonus and other neuroexcitatory effects within 24 hours, while achieving comparable pain control.
Rotation is especially important in patients with opioid-induced hyperalgesia.
As a general rule, decrease the morphine equianalgesic dose by at least 50% when switching to a new medication. For patients on very high doses, rotate to a new opioid at 20-25% of the morphine equianalgesic dose. Historically, methadone
have been considered to be better opioids to rotate to as they have no active metabolites. Note
: when switching to methadone it is advisable to review recent methadone
Adjuvant and other analgesic therapy
Adjuvant analgesics (e.g. anticonvulsants, antidepressants, corticosteroids) or non-drug therapies (e.g. acupuncture, TENS, heat, cold) may allow for opioid reduction, with preservation of analgesia.
Benzodiazepines and other drugs to reduce myoclonus
The addition of a benzodiazepine may reduce myoclonus without alteration of the opioid dose, although increasing sedation may be an unwanted side effect. Start with clonazepam
0.5-1mg qhs or 0.5mg BID or TID. Alternative agents include lorazepam
orally or sublingually, starting at 1-2mg q8. Continuous infusion midazolam
is an effective option.
Alternatives to benzodiazepines include baclofen, gabapentin, and nifedipine. Start baclofen
at 5 mg 3 times a day and increase as needed/tolerated to 20 mg 3 times a day. Start gabapentin
at 100 mg 3 times a day and increase as needed to 900-3600 mg total a day. Nifedipine
(10 mg 3 times a day) can also be used.
Adapted from Wilson RK and Weissman DE. Palliative Care Network of Wisconsin. Fast facts and concepts #58. Neuroexcitatory effects of opioids: treatment. Internet. Accessed on January 25, 2016.