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Epic Test Code LAB31 Phenytoin, Total, Serum

Synonyms

Dilantin, Diphenylhydantoin

Performing Location(s)

BMC,FOX,FTT,CRH,LFH,OCH

Specimen Type

Serum 

Preferred Container

Red top tube

Blood Tube Draw Volume

Min 50% draw volume  

Minimum Volume to Submit for Testing

0.5 mL Serum

  • Multiple test can be performed from this volume. For question please contact the lab at 547-3975.  

Storage Requirements

Sample tubes should be centrifuged within 1 hour of collection followed by transfer of the serum to a labeled plastic, aliquot tube

 

Transportation Needs

 Deliver specimen to laboratory within 1 hour of collection if unspun. If not possible see "storage Requirements". 

Causes for Rejection

Mislabeled or unlabeled specimen
Less than 50% draw for Vacutainer tubes

Anything other than a red top tube
Hemolysis >800 mg/dL HgB
Lipemia >750mg/dL Trig
Bilirubin >30 mg/dL Bili
> 1 month refrigerated (Serum tubes are routinely stored at the lab for only 7 days therefore, an add-on may not be possible after 7 days.)
> 24 hours room temperature
> 3 months Frozen
Heparin,EDTA,NaF,Cit

Reference Values

Population Units Therapeutic Range High Critical Value
General ug/mL 10.0 - 20.0 > 25.0

 

Available STAT

Yes

Days of Analysis

All

Additional Information

Additional Information:

Because of considerable inter-individual variation and the limited capacity for the liver to metabolize phenytoin, blood concentrations should be monitored to obtain maximal anti-seizure effect. Once metabolism is saturated, small dosage changes may result in disproportionate changes in blood concentration and can cause wide variations in dosage requirements among patients.

 

Collection Guideline:

Collect after steady state conditions are reached, i.e. after 4-5 half-lives on unchanged dose regimen.

 

Collect samples following oral dosing immediately prior to next dose for drugs with short half lives. For drugs with long half-lives, ≥24 hours, draw time is less critical.

 

Obtain samples following IV dosing of phenytoin at 1-4 hours post dose.

 

After administration of fosphenytoin, collect specimens 2 hours post IV or 4 hours post IM dose.

 

Collect within 6 hours after a seizure in previously controlled patient

Methodology

Beckman AU/Dx Series

CPT Code

80185

Last Updated

19-DEC-24 MS