Phenytoin (Dilantin) Correction for Albumin/Renal Failure
Corrects serum phenytoin level for renal failure and/or hypoalbuminemia.
Use in patients with albumin ≤3.2 g/dL (32 g/L). The “Sheiner-Tozer Equation” is the official name of this correction. This updated formula uses an albumin coefficient of 0.275, and 0.2 for patients with renal failure (see Evidence for details).
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Adjust phenytoin dosing based on values.
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If consistently out of range, consider other antiepileptics.
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Concomitant use of valproic acid and some other drugs displaces phenytoin from plasma proteins and can lead to erratic levels.
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Whenever possible, a free phenytoin level should be utilized over a corrected level.
A therapeutic phenytoin level is generally considered to be 10-20 mg/L (40-80 µmol/L). Levels above this may cause nystagmus, ataxia, lethargy, confusion, and coma.