The Cardiovascular
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Phenytoin Correction for Albumin/Renal Failure

Adjusts total phenytoin level for hypoalbuminaemia.

Phenytoin Correction for Albumin/Renal Failure
Measured total phenytoin
mcg/mL
Serum albumin
Renal function
Complete the fields above to see the result.

When to use

  • Interpreting a total phenytoin level in a hypoalbuminaemic patient.
  • Adjusting for reduced protein binding in renal failure.

Formula

Corrected = measured / (0.2 x albumin + 0.1). In renal failure (CrCl <10): Corrected = measured / (0.1 x albumin + 0.1). Albumin in g/dL.

Pearls and pitfalls

  • A directly measured free (unbound) phenytoin level is preferred when available.
  • The correction assumes a normal reference albumin of about 4.4 g/dL.

References

  1. Winter ME, Tozer TN. Phenytoin. In: Evans WE, et al. Applied Pharmacokinetics. 3rd ed. 1992. (Winter-Tozer / Sheiner-Tozer equation.)