Pathology Handbook

 New search
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # ALL

Phenytoin, free

Alternative Names:Free Phenytoin
Laboratory:Clinical Biochemistry
Test Code:FREEPTN
Specimen Types:Blood
Container Types:
Lithium Heparin (with Gel)
SST
Adults Volume or Mass:2 mL
Minimum/Paediatric Volume or Mass:1 mL
Collection & Request Instructions:

Collect pre-dose.

Transport Instructions between Sites and/or Laboratories:Room Temperature
Additional Notes:

Where plasma albumin is reduced, free phenytoin may provide a better indication of drug toxicity than total (measured) phenytoin.

"Albumin-adjusted phenytoin" and "Free phenytoin" are calculated using the modified Scheiner-Tozer equation taking into account renal function and assuming 90% protein binding.

Ref:  Chesher D. Calculated free Phenytoin and Albumin adjusted Total Phenytoin versus measured free phenytoin. Pathology vol 51, Supp 1, S108, Feb 2019