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Test Code PHYT Dilantin Level

Additional Codes

Cerner

NextGen

Dilantin Level

Dilantin Level

Phenytoin Level

 

Alternate Name(s)

Phenytoin Level

Methodology

Enzymatic Heterogenous CIA, Multiple-point immuno-rate

Patient Preparation

None

Collection Instructions

  • Standard phlebotomy practices.
  • Specimen collection times:
    • Monitor long term therapy – just before next dose.
    • Adequate therapy - just before next dose.
    • Possible toxicity – 6 hours after last dose or up to 8 hours if drug is given with substances that increase stomach acidity.

Specimen Requirements

Container

Specimen Type

Tube

Lithium Heparin Plasma

Serum

 or 

SST

For up to 24 hours

 or  or 

 

Stability

Storage

Temperature

Stability

Room Temperature

18-28°C

≤ 8 hours

If separated within 4 hours

Refrigerated

2-8°C

≤ 7 days

If separated within 4 hours

Frozen

≤ -18 °C

≤ 12 weeks

If separated within 4 hours

Rejection Criteria

Gross Hemolysis

Result Reporting and Reference Values

Reported in µg/mL        

Age

Low

High

Critical Low

Critical High

Therapeutic Range

10.0

20.0

N/A

>30.0

Reflex Testing

None

Limitations

  • Ortho reports a bias with the following:
    • Total Protein >9.0 g/dL have been shown to cause a bias >2.3 µg/mL
    • Bilirubin (Bc) at 20 mg/dL has been shown to cause bias of +7.8 µg/mL
    • Ethamsylate 3.0 mg/dL has been shown to cause a bias of +7.1 µg/mL
    • Gentisic acid at 5.00 mg/dL has been shown to cause a bias of 9.6 µg/mL
    • Hemoglobin at 200 mg/dL has been shown to cause a bias -5.9 µg/mL
  • Ortho reports no significant effect with the following: 
    • Lipemia up to 800 mg/dL
  • The following interpretive data is visible to pracitioner:
    • Total protein >9.0 g/dl may give a positive bias. The following drugs at therapeutic levels may interfere with phenytoin determination creating a positive bias; Ethamsylate, Gentisic acid, Hypaque, N-acetylcysteine

Useful For

Phenytoin (Dilantin) is a widely prescribed anticonvulsant drug used in the treatment of generalized and partial seizures. Phenytoin measurements are used to monitor patient compliance and therapy and to diagnose potential overdose.