Lab reference

Phenytoin Level

Drug Levels

For education. Check every result.

Anatium is a study resource, not medical advice. Nothing here is a diagnosis, a prescription or a substitute for a clinician who has seen the patient. Check every number against a current local protocol before it touches anyone, and never act on a result you cannot reproduce yourself.

Reference range

Range10 to 20 mg/L

About

Serum phenytoin. Its kinetics are non-linear, so a small dose increase can produce a large level jump, and a low albumin makes the total level read falsely low.

When it is low

Subtherapeutic: seizure risk

When it is high

Nystagmus at 20, ataxia at 30, confusion above 40. zero-order kinetics mean a small dose rise can cause a large level rise. Correct for albumin

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