From the Guidelines
Opioid-induced segmental myoclonus should be managed by reducing or discontinuing the causative opioid when possible, and if opioid therapy must continue, switching to a different opioid may help, as cross-sensitivity varies between agents, according to the most recent guidelines 1.
Management of Opioid-Induced Segmental Myoclonus
The management of opioid-induced segmental myoclonus typically involves reducing or discontinuing the causative opioid when possible. If opioid therapy must continue, switching to a different opioid (opioid rotation) may help, as cross-sensitivity varies between agents.
Medications for Myoclonus Suppression
Benzodiazepines such as clonazepam or diazepam are often effective in suppressing myoclonus. Other helpful medications include baclofen, dantrolene, or levetiracetam.
- Key medications for myoclonus suppression:
- Benzodiazepines: clonazepam (0.5-2mg daily) or diazepam (5-10mg daily)
- Baclofen: 10-25mg three times daily
- Dantrolene: 25-100mg daily
- Levetiracetam: 500-1500mg twice daily
Supportive Measures
Hydration and correction of metabolic abnormalities are important supportive measures. This condition occurs because opioids can disrupt the balance of inhibitory and excitatory neurotransmitters in the central nervous system, particularly affecting GABA pathways and spinal cord interneurons, as noted in the management of delirium and neurotoxicity 1.
Risk Factors
Patients with renal impairment, the elderly, and those on high opioid doses are at increased risk. The myoclonus typically resolves completely once the triggering medication is adjusted or discontinued, though it may take several days for symptoms to fully resolve.
From the Research
Opioid-Induced Segmental Myoclonus
- Opioid-induced myoclonus is a condition that can occur in patients undergoing opioid therapy, with the pathophysiology not yet fully elucidated 2.
- Studies have shown that opioid-induced myoclonus can be dose-related, but in an unpredictable manner 3.
- The condition can be characterized by sudden, brief, and involuntary movements of segmental or propriospinal muscle groups 2.
Treatment Options
- Treatment of myoclonus requires an understanding of the physiopathology of the condition, and may involve a review of medications and comorbidities to establish the possibility of iatrogenic and reversible conditions 4.
- In some cases, continuous intrathecal morphine infusion has been shown to relieve spinal myoclonus entirely 2.
- However, high spinal morphine doses in conjunction with pathological changes within the spine can also be risk factors for the development of myoclonus, spastic muscle tone, and spinal jerking 5.
- Adjuvant drugs, such as benzodiazepines or dantrolene, may be used to avoid the reduction of the opioid dose while maintaining acceptable analgesia 3.
Case Reports
- A case report described a 76-year-old man who developed myoclonic jerks and hyperalgesia after receiving a short course of low-dose oral opioids, which resolved after discontinuation of the opioids 6.
- Another study reported two patients with spinal segmental myoclonus secondary to ischemic and radiation myelopathy, who responded to continuous intrathecal morphine infusion 2.