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Test Code Phenytoin Phenytoin Level

Important Note

No add-ons after 8 hours of collection if specimen is still on gel separator.

Clinical System Name

Phenytoin Level

Synonyms

Cerebyx
Dilantin
Diphenylhydantoin
DPH
Fosphenytoin

Description

Phenytoin 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.

Sample Requirements

Specimen:  Whole Blood

Container(s):  Gold SST, Red Tube,  Lt. Green/Lithium Heparin Microtainer, Gold Microtainer, or Dark Green/Sodium Heparin

Preferred Vol:  1.0 mL

Minimum Vol:  0.5 mL  

 

Note:  Draw specimen just before next dose.  Avoid hemolysis.This test is a total Phenytoin (Dilantin). Free Phenytoin requires 6 mL blood; if ordered, both the free and total will be performed at Harborview with a turn-around time of 1 - 3 days. 

 

Processing Instructions

Reject due to: Hemolysis, age of specimen, incorrect collection container.

Spin: Y

Aliquot: Y

Temp:  2-8oC

Storage location:  Core Chemistry Refrigerator

 

Off-site collection:  Draw specimen just before next dose. Avoid hemolysis. Spin blood, freeze serum or plasma.

Stability

 

Specimen Type Temperature Time
Serum or Plasma RT

8 H

Serum or Plasma 2-8oC

7 D

Serum or Plasma -20o C or -70oC

12 W

 

Availability

STAT Performed TAT
Y 24/7 1 H

 

Performing Laboratory

Seattle Children's Laboratory    

Department

Department:  Core Chemistry

Phone Number: 206-987-2617

 

 

Reference Range

 

  uG/mL
Therapeutic 10 - 20
Toxic

≥  25

 

Methodology

Method:  Immunassay method by Vitros 4600

Analytical Volume: 0.02 mL serum or plasma + 0.03 mL dead space

MinimumVolume: 0.05 mL serum or plasma

 

Method is affected by EDTA & hemolysis.

CPT Codes

80185

Critical Values

≥ 25 uG/mL