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PhenytoinAdjusted = PhenytoinMeasured /((SerumAlbumin * RenalFx ) + 0.1)


  • Equation parameters such as Renal Fx have two or more discrete values that may be used in the calculation. The numbers in the parentheses, e.g. (0.2), represent the values that will be used.
  • This calculator is used to predict the total phenytoin level (adjusted for hypoalbuminemia and renal function) that is commonly used for phenytoin dosage adjustment.
  • To predict the unbound, free phenytoin level in patients with hypoalbuminemia, please see the calculator Phenytoin Free (Unbound) Drug Level (Adjusted for Hypoalbuminemia.)


  1. Wolf GK, McClain CD, Zurakowski D, Dodson B, McManus ML. Pediatr Crit Care Med. 2006 Sep; 7(5):434-9; quiz 440.
  2. Clinical decision support of therapeutic drug monitoring of phenytoin: measured versus adjusted phenytoin plasma concentrations. BMC Med Inform Decis Mak. 2012 Feb 14; 12:7.

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