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HelpTest ID FELBA Felbamate (Felbatol), Serum
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
Method Name
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Reporting Name
Felbamate (Felbatol), SSpecimen Type
SerumContainer/Tube:
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 1 mL
Collection Instructions: Draw specimen immediately before next scheduled dose.
Forms: If not ordering electronically, complete, print, and send a Neurology Test Request Form-General (T732) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/neurology-request-form.pdf)
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 28 days |
| Ambient | 28 days | |
| Frozen | 28 days |
Clinical Information
Felbamate is an anticonvulsant drug approved for treatment of partial seizures with or without secondary generalization in persons >14 years of age. It is also approved for Lennox-Gastout syndrome in children >2 years of age. 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 13 to 23 hours.
Optimal response to felbamate is seen with serum concentrations between 30 mcg/mL to 60 mcg/mL. Patients who are elderly or have renal 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, but no defined toxic concentration has been established.
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.
Reference Values
30.0-60.0 mcg/mL
Cautions
No significant cautionary statements
Day(s) Performed
Monday, Wednesday, Friday; 3 p.m.
Report Available
Same day/1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
80299