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Test Code FELBA Felbamate (Felbatol), Serum

Reporting Name

Felbamate (Felbatol), S

Useful For

Determining whether a poor therapeutic response is attributable to noncompliance or lack of drug effectiveness

 

Monitoring changes in serum concentrations resulting from interactions with coadministered drugs such as barbiturates and phenytoin

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Supplies: Sarstedt Aliquot Tube 5 mL (T914)

Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collection Instructions:

1. Draw blood immediately before next scheduled dose.

2. Within 2 hours of collection, centrifuge the specimen.

3. For red-top tubes, immediately aliquot serum into a plastic vial.

4. For serum-gel tubes, aliquot serum into a plastic vial within 24 hours of collection.


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

80167

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FELBA Felbamate (Felbatol), S 6899-9

 

Result ID Test Result Name Result LOINC Value
80782 Felbamate (Felbatol), S 6899-9

Clinical Information

Felbamate is an anticonvulsant drug approved for treatment of partial seizures with or without secondary generalization in persons 14 years and older. It is also approved for Lennox-Gastout syndrome in children 2 years and older. Felbamate is well absorbed (>90%) and is metabolized by the hepatic cytochrome P450 system. Metabolites lack anticonvulsant activity. The elimination half-life of felbamate ranges from 16 to 22 hours.

 

Optimal response to felbamate is seen with serum concentrations between 30 mcg/mL to 80 mcg/mL. Patients who are older adults or have kidney dysfunction may require reduced dosing; felbamate should not be given to individuals with hepatic disease. Toxicity can be severe, including life-threatening aplastic anemia or liver failure; toxic concentration has been established at concentrations greater than 100 mcg/mL.

 

Coadministration of felbamate increases the concentration of phenytoin and valproic acid, decreases carbamazepine concentration, and increases carbamazepine-10,11-epoxide (its active metabolite). Conversely, coadministration of phenytoin or carbamazepine causes a decrease in felbamate concentration.

Cautions

No significant cautionary statements

Report Available

Same day/1 to 3 days

Specimen Retention Time

14 days

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Day(s) Performed

Monday, Wednesday, Friday

Forms

If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Neurology Specialty Testing Client Test Request (T732)

-Therapeutics Test Request (T831)

Secondary ID

80782