Phenobarbital CSCI Dosing — SCE Palliative Medicine MCQ

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ModerateSyringe Driver & Drug CompatibilityPhenobarbital CSCI DosingSCE Palliative Medicine

A patient on a CSCI with morphine 40mg and midazolam 10mg/24hr develops breakthrough seizures. Midazolam is increased to 40mg/24hr without effect. Phenobarbital is started via a separate CSCI. What is the usual starting dose of SC phenobarbital for refractory seizures/agitation at end of life?

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Correct answer: C — Phenobarbital 600–1200mg/24hr via separate CSCI, with a 200mg loading dose IM/IV if seizures are acute

Option C is correct: UK palliative care guidance recommends a loading dose of phenobarbital 200mg IM/IV, repeatable as needed acutely, followed by a maintenance dose via a separate CSCI at 400–1200mg/24hr (frequently 600–1200mg/24hr in refractory cases). Option B (100mg/24hr), C (50mg/24hr), and D (10mg/24hr) represent subtherapeutic doses that will not control seizures; option E (3000mg/24hr) significantly exceeds guideline maxima, risking deep unconsciousness or toxicity. The stem's focus on refractory symptoms and CSCI separation matches guideline recommendations.

Reference: Right Decisions – Scottish Palliative Care Guidelines: Phenobarbital (Phenobarbitone), current, https://www.rightdecisions.scot.nhs.uk/scottish-palliative-care-guidelines/medicines-information/phenobarbital-phenobarbitone/