Umstead and Neumann used a simple equation to predict the percent free phenytoin in a patient with cancer based on the serum albumin. The authors are from William Beaumont Hospital and Wayne State University.
Parameters:
(1) serum albumin in grams per L (g/L, not g/dL)
(2) serum total phenytoin concentration in mg/L
percent free phenytoin =
= 34.54 - (0.65 * (serum albumin in g/L))
free serum phenytoin in mg/L =
= (total serum phenytoin) * (percent free phenytoin)
The prediction may be suboptimum if:
(1) the patients is taking one or more medications that would displace phenytoin from albumin
(2) the patient is in the hospital or has severe comorbid conditions
In these situations direct measurement of the free phenytoin concentration should be performed.
To read more or access our algorithms and calculators, please log in or register.
Specialty: Toxicology, Emergency Medicine, Critical Care, Neurology
ICD-10: ,
