A 50-year-old man on ICU is receiving IV phenytoin for post-traumatic seizures. His serum albumin is 20 g/L. Total phenytoin level is 7 mg/L (therapeu...

Question

A 50-year-old man on ICU is receiving IV phenytoin for post-traumatic seizures. His serum albumin is 20 g/L. Total phenytoin level is 7 mg/L (therapeutic range for total: 10-20 mg/L). The pharmacist corrects this for hypoalbuminaemia using the Sheiner-Tozer equation: Corrected = Measured / (0.2 × albumin [g/dL] + 0.1). Albumin = 2.0 g/dL. Corrected = 7 / (0.2 × 2.0 + 0.1) = 7/0.5 = 14 mg/L. What does this corrected level indicate?

Accepted Answer

The corrected level of 14 mg/L is within the therapeutic range (10-20 mg/L) - the total level appeared subtherapeutic because hypoalbuminaemia reduces protein binding, lowering total drug while maintaining adequate free (active) drug; the dose should NOT be increased based on the low total level alone

Answer

The patient needs a higher phenytoin dose

Answer

The correction is unnecessary

Answer

Switch to a different anticonvulsant

Answer

The corrected level is toxic

uk-fficm MCQ (SBA): Phenytoin - Albumin Correction