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    Phenytoin/Dilantin Correction for Albumin / Renal Failure

    Corrects a phenytoin serum level for renal failure and/or hypoalbuminemia.
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    Pearls/Pitfalls

    Phenytoin has a narrow therapeutic window, and is highly protein bound. The protein bound phenytoin is what is typically measured by the lab. However unbound phenytoin is the active portion (it crosses the blood-brain barrier). This calculator helps estimate the equivalent active amount of phenytoin based on typical lab values.

    µg/mL
    g/dL

    Result:

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    Advice

    • Adjust phenytoin dosing based on values.
    • If consistently out of range, consider other antiepileptics.

    Formula

    Corrected Phenytoin = Measured Phenytoin Level / ( (adjustment x albumin) + 0.1)

    Adjustment = 0.2; In patients with Creatinine Clearance < 20, adjustment = 0.1.

    Facts & Figures

    The “Sheiner-Tozer Equation” is the official name of this correction.

    Dr. Thomas N. Tozer

    About the Creator

    Thomas N. Tozer, PhD, PharmD, BS, is professor emeritus of biopharmaceutical sciences and pharmaceutical chemistry at School of Pharmacy at UCSF. He is the co-author of Clinical Pharmacokinetics and Pharmacodynamics: Concepts and Applications. Prior to retirement, Dr. Tozer researched colon-specific drug delivery, toxicokinetics, kinetics of potential contrast agents for magnetic resonance imaging and nonlinear pharmacokinetics.

    To view Dr. Thomas N. Tozer's publications, visit PubMed