Phenytoin Level


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


Collection Instructions

Specimen:Blood
Optimal Volume:2.5 mL
Minimum\Peds Volume:0.6 mL
Container:Red (no gel)
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. Fosphenytoin is measured as total phenytoin, Order PHYT with comment "Fosphenytoin".


Processing and Shipping

Specimen Processing:Centrifuge and transfer serum within 2 hours of collection. Aliquot 1.25 mL, 0.3 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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