Myoclonus & Seizures


Muscle jerks in several muscle groups/limbs.
May be a sign of opioid neurotoxicity.

If combined with other symptoms of opioid neurotoxicity (sedation, confusion, hallucinations, agitation) rotate opioid. See Manage pain Opioid Calculations
If patient in last hours to days of life manage myoclonus with midazolam 1-5mg sc q1hr prn or lorazepam 0.5-2mg q6-8hrs prn


Immediate therapy:

  • midazolam 5-10mg sc/iv/im q10 minutes until stopped
  • lorazepam 1-2mg sc/iv/im q10 min until stopped

Status epilepticus: if seizure persists after 3 doses of above add Phenobarbital 100mg sc. May need midazolam or lorazepam infusion if persists
Prevention of further seizures: Phenytoin 300mg q2 hrs X 3 doses to load. Maintenance dose 300-400mg once daily depending on response and side effects. For severe renal function reduce dose by 50%. Blood levels just before next dose 5 days after initiation or dosage change. Beware drug interactions