Phenytoin – Hypoalbuminaemia — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

HardEpilepsy & Seizure DisordersPhenytoin – HypoalbuminaemiaSCE Neurology

A 55-year-old man with epilepsy on phenytoin has a level of 15 mg/L with albumin of 20 g/L. Is the level reliable?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — No — with low albumin, the free (active) fraction is increased; a total of 15 with albumin 20 may correspond to toxic free levels; measure free phenytoin level

Phenytoin is ~90% protein-bound to albumin. Low albumin increases the free fraction. Total level may appear 'therapeutic' while free level is toxic. Use the Winter-Tozer correction or measure free level directly. A: Misleading with low albumin. C: Increasing risks toxicity. D: Albumin significantly affects interpretation. E: Albumin, not calcium.

Reference: BNF – Phenytoin TDM; NICE NG217