Corrected Phenytoin Level
Corrects total phenytoin level for hypoalbuminaemia. Phenytoin is ~90% protein-bound — low albumin causes falsely low total levels. Used in epilepsy management and toxicity assessment.
Score interpretation
Corrected phenytoin < 10 mg/L: Below therapeutic range (10–20 mg/L).
→ Seizure risk increased. Review adherence and dose. Increase phenytoin dose cautiously (small increments due to saturable kinetics). Recheck level in 1–2 weeks.
Corrected phenytoin 10–20 mg/L: Therapeutic range. Optimal seizure control expected.
→ Continue current dose. Annual level monitoring or after dose changes. Monitor for toxicity signs (nystagmus, ataxia, diplopia).
Corrected phenytoin 20–30 mg/L: Above therapeutic range. Early toxicity possible.
→ Check for nystagmus (typically at 20 mg/L), ataxia (> 30 mg/L), mental status changes. Consider dose reduction. Review for drug interactions.
Corrected phenytoin > 30 mg/L: Toxic. Risk of severe CNS toxicity.
→ Hold phenytoin dose. Supportive care. Monitor for cerebellar toxicity (ataxia, nystagmus, dysarthria), cardiovascular toxicity (bradycardia, hypotension if IV). Repeat level in 24h.
Interpretation bands for the Corrected Phenytoin. Apply clinical judgement and local guidance.
References
- Winter ME, Tozer TN. Phenytoin. In: Applied Pharmacokinetics: Principles of Therapeutic Drug Monitoring. 3rd ed. Applied Therapeutics, 1992.
Related
Curated clinical cross-links plus same-class fallbacks.
- Hydroxychloroquine (Ophthalmic Toxicity Monitoring) · Antimalarial — Ophthalmic Toxicity Monitoring Drug
- Phenylephrine · Alpha-1 Adrenergic Agonist (Pure Vasoconstrictor)
- Hydrocortisone (ICU — Stress Dosing) · Corticosteroid (ICU/Septic Shock)
- Phenytoin / Fosphenytoin · Antiepileptic — Status Epilepticus (Second-Line)
- Carbimazole · Antithyroid Drug
- Zoledronic Acid · Bisphosphonate (IV)
- Acute Stroke / TIA Assessment · NICE NG128; RCP Stroke Guidelines 2023
- Status Epilepticus (Adults) · NICE CG137; ESEM guidelines; RCP Neurology Guidelines
- Suspected Subarachnoid Haemorrhage · NICE NG228; RCEM 2023; AHA/ASA 2023
- Adult Head Injury · NICE NG232 (2023)
- Bell's Palsy / Facial Nerve Palsy · ENT UK 2017; AAN
- Vertigo Workup · ENT UK; NICE CKS
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.