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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Felbamate

Test Code(s): FELB / XFELB

CPT Code(s): 80299

Methodology: Gas Chromatography

Clinical Significance: Anticonvulsant

Days Performed: Mon-Fri, dayshift.

Turnaround Time: Routine: 24 hours.


Specimen Requirements

Specimen: Blood

Collection Instructions: Collect specimen for trough level prior to next dose.

Collection Container: Preferred: Red top

Collection Volume: Preferred: 9 mL
Pediatrics: 3 mL

Sample Analyzed: Serum

Volume Required: Preferred: 2 mL
Pediatrics: 1 mL

Specimen Processing: Centrifuge. Transfer cell-free serum to plastic vial.

Specimen Transport: Transport specimen to UWHC Core Laboratory (B4/220). Transport with coolant pack if coming from outreach location.

Unacceptable Criteria: Specimens collected in red cap with yellow ring (SST) tubes are not acceptable.

Stability: Ambient: 8 days
Refrigerated: 30 days
Frozen: 14 days


Interpretation

Interpretive Guidelines:

Definitive therapeutic concentration for felbamate has not been established. A serum concentration of 40-80 mcg/mL is generally considered to be therapeutic for individuals 18 years old and up. Trough serum concentrations are dose proportional. Multiple daily doses of 1200, 2400, and 3600 mg gave trough serum concentrations of 30 +/- 5, 55 +/- 8, and 83 +/- 21 mcg/mL, respectively, in adults. (Data from Wallace Laboratories, Cranbury, NJ 08512).

Critical Calls: View

Additional Information:

Felbamate is excreted with a terminal half-life of 20-23 hours, which is unaltered after multiple doses. Active metabolites have not been reported. Co-administration of felbamate will alter steady-state serum concentrations of phenytoin, carbamazepine, and valproate as follows: Increase phenytoin, valproate and possibly phenobarbital concentrations. Decrease carbamazepine, and increase of carbamazepine 10,11-epoxide concentrations. Addition of carbamazepine and/or phenytoin to the regimen of a patient on felbamate monotherapy will decrease the serum felbamate concentration. Valproate can increase the concentration of felbamate. It is recommended for patients on felbamate and carbamazepine that the carbamazepine and 10,11-epoxide be monitored.

 

This test was developed and its performance characteristics determined by the UWHC Clinical Laboratories.  This test meets the standards for clinical testing.  This test should not be regarded as investigational or for research use.  The US Food and Drug Administration (FDA) has not approved or cleared this test; however, the FDA has determined that such clearance or approval is not necessary.

Felbatol

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