Phenobarbitone as pharmacotherapy for refractory myoclonus in intubated dying patients, a case series

Otway, Victoria, McKenzie, Cathrine and Davis, Carol (2025) Phenobarbitone as pharmacotherapy for refractory myoclonus in intubated dying patients, a case series. Palliative Care Congress, , Belfast, United Kingdom. 03 - 07 Mar 2025. (doi:10.1136/spcare-2025-PCC.202).

Abstract

Background University Hospitals Southampton (UHS) palliative care team works closely with the general intensive care unit (GICU) to care for patients post cardiac arrest with significant myoclonic activity causing family member distress.Our aim was to establish whether phenobarbitone had application as pharmacotherapy for refractory myoclonus in intubated dying patients. Methods Retrospective observational analysis; cases identified by searching the clinical information system for prescription of phenobarbitone.Data collected onset of myoclonus, phenobarbitone prescription and myoclonus cessation as well as name, dose and route of medication used before or alongside phenobarbitone. Results 12 patients had phenobarbitone administered; 3 had status epilepticus. The remaining 9 had myoclonus secondary to hypoxic brain injury, refractory to drugs including levetiracetam, midazolam, phenytoin and valproate. All were intubated and ventilated and were dying with extubation planned. At least 7 had an intravenous (IV) loading dose (100 to 1000mg); in a minimum of 6, this was followed by a continuous infusion (again 200 to 1000mg) either subcutaneously or intravenously, depending on access.Median onset of myoclonus to first phenobarbitone administration 112 hours; mean 107 hours; range 85 hours to 167 hours. Time from first phenobarbitone administration to myoclonus control was poorly recorded; median 5 hours; mean 8 hours; range immediate to 22 hours. We were informed some patients responded quicker than recorded. In all cases, family members were able to say goodbye after myoclonus had stopped and before extubation. Conclusion Phenobarbitone appears to be an efficacious pharmacotherapy for refractory myoclonus which makes the dying process less distressing for families.Currently we administer an IV loading dose of 10mg/kg followed by a 10mg/kg continuous infusion over 24 hours. Further case reports may allow consensus of dosing and schedule for phenobarbitone for this indication. Accurate recording of timing of myoclonus cessation is essential.

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Contributors

Author: Cathrine McKenzie

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