Phenytoin Total Drug Level (Adjusted for Hypoalbuminemia and Renal Function)

 

Input
 

Phenytoin Measured		mcg/mL mcmol/L mg/L micromole/L
Renal Fx	Adequate Renal Function (0.2)
	Creat Clearance <10 mL/min (0.1)
Serum Albumin		g/L g/dL gm/L gm/dL mg/L mg/dL

 
Result
 
Important: Inputs must be complete to perform calculation.

 

Phenytoin Adjusted		mcg/mL mcmol/L mg/L micromole/L
Decimal Precision   0 1 2 3

 

 

Notes

• In this calculator, mcg is the abbreviation for micrograms.
• 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.)

 
Equations used
 

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.
 

 

References

1. Martin E, Tozer TN, Sheiner LB, Riegelman S. The clinical pharmacokinetics of phenytoin. J Pharmacokinet Biopharm. 1977 Dec;5(6):579-96.
2. Dasgupta A, Dennen DA, Dean R, McLawhon RW. Prediction of free phenytoin levels based on [total phenytoin]/[albumin] ratios. Potential errors with hypoalbuminemia. Am J Clin Pathol. 1991 Feb;95(2):253-6.
3. Kiang TK, Ensom MH. A Comprehensive Review on the Predictive Performance of the Sheiner-Tozer and Derivative Equations for the Correction of Phenytoin Concentrations. Ann Pharmacother. 2016 Apr;50(4):311-25.