Phenytoin Correction for Albumin / Renal Failure
Corrects total phenytoin level for hypoalbuminaemia and/or renal failure to estimate free (active) phenytoin concentration. Therapeutic range for free phenytoin: 1–2 mg/L.
Score interpretation
Corrected phenytoin below therapeutic range (10–20 mg/L).
→ Consider dose increase. Assess seizure control and adherence. Re-check levels after dose change.
Corrected phenytoin within therapeutic range (10–20 mg/L).
→ Continue current dose. Regular level monitoring every 3–6 months or with dose changes.
Corrected level mildly elevated. May see nystagmus at higher levels.
→ Review dose. Assess for signs of toxicity (nystagmus, ataxia, sedation). Reduce dose cautiously.
Corrected level in toxic range. Risk of serious adverse effects.
→ Hold phenytoin. Assess for ataxia, diplopia, dysarthria, mental status changes. Supportive care. Consider alternative anticonvulsant.
Interpretation bands for the Phenytoin Correction. Apply clinical judgement and local guidance.
References
- Winter ME. Basic Clinical Pharmacokinetics. 5th ed. Lippincott Williams & Wilkins; 2009.
- Tozer TN, Winter ME. Phenytoin. In: Applied Pharmacokinetics: Principles of Therapeutic Drug Monitoring. 3rd ed. 1992.
Related
Curated clinical cross-links plus same-class fallbacks.
- Fosphenytoin sodium · Phenytoin prodrug (anticonvulsant)
- Vancomycin (Renal Dosing) · Antibiotic Dosing in CKD
- Gentamicin (Renal Dosing/TDM) · Antibiotic Dosing in CKD
- Mannitol (Osmotic Diuretic — Renal/Neurological) · Acute Oliguric Renal Failure / Raised ICP
- Phenylephrine · Alpha-1 Adrenergic Agonist (Pure Vasoconstrictor)
- Hydrocortisone (ICU — Stress Dosing) · Corticosteroid (ICU/Septic Shock)
- 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.