PHENYTOIN, TOTAL AND FREE - (S)
Test Code: MISC
This test is used for monitoring both total and free phenytoin in patients with renal failure.
In uremia, by-products of metabolism accumulate and bind to albumin, displacing phenytoin, which causes an increase in the free (active) fraction. In renal failure, the ability to clear the free phenytoin fraction is also significantly reduced. Both the total and free concentration of phenytoin increase, with the free fraction rising faster than the total. Dosage must be adjusted to avoid toxicity. The free phenytoin level is therefore the best indicator of adequate therapy in renal failure.
Must be approved by a Clinical Chemist prior to sendout.
Click here for the Approval For Test Referral Biochemistry (F260-11-02)
Send referral request form and a test requisition specifying Phenytoin, Total and Free to be sent to Mayo Laboratories. Do not use the phenytoin check box on the requisition.
Serum: 2.0 mL
Pediatric Serum: 1.0 mL
Centrifuge and aliquot within 2 hours of collection
Stability 7 days refrigerated, 14 days frozen
Serum: 2.0 mL
Store and ship frozen
Therapeutic: 10 - 20 mg/L
Toxic: > 20
Therapeutic: 1.0 - 2.0 mg/L
Toxic: > 2.0
Within 1 Week
Store and ship serum refrigerated (preferred) or frozen to Mayo Medical Laboratories.
Test ID: PNTFT
Manufacturer: Becton Dickinson
Catalogue #: 366430