Phenytoin Level


Sunquest Code:PHYT  
Epic Code:LAB31Epic Name:Phenytoin Level
Synonyms:Dilantin; Diphenylhydantoin; Fosphenytoin; Phenytoin; PHYT
Methodology:Turbidimetric rate
CPT Code:----------CPTCODES HERE----------
Turnaround Time:Performed and reported 24 hours/day.


Collection Instructions

Specimen:Blood
Optimal Volume:2.5 mL
Minimum\Peds Volume:0.6 mL
Collection Instructions:Trough level is preferred; collect immediately before dose. It is advisable to monitor at the same time in the dosing schedule. Collect peak level 1.5-3 hours after solid dosage (rapid dissolution) formulation or 3-9 hours after extended dissolution.
Causes for Rejection:Collected in a gel tube, collected in a purple (EDTA) tube.
Contraindications:Fosphenytoin, a phosphate ester of phenytoin, cross-reacts with this assay. Samples from patients receiving fosphenytoin should be collected at least 2 hours following IV administration or 4 hours following IM administration. Phenytoin levels measured before complete conversion of fosphenytoin will not reflect phenytoin concentrations ultimately achieved.


Processing and Shipping

Specimen Processing:Centrifuge and transfer serum/plasma within 2 hours of collection. Aliquot 1.25 mL, 0.2 mL minimum. Store in refrigerator.
Shipping Instructions:Ship at refrigerated temperature.
Test Performed at or Referral Lab Chemistry  (Fairview Range - FRMC, UMMC-East Bank, Fairview Lakes - FLMC, Fairview Ridges - FRH, Fairview Southdale - FSH, UMMC/UMMCH-West Bank)


Interpretive

Critical Range:Greater than 30 mg/L
Therapeutic Range:10-20 mg/L
Use:Monitor therapeutic dosing and evaluate toxicity. Half-life is 8-60 h.


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