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Evaluate toxicity; monitor therapeutic levels
Liquid chromatography/tandem mass spectrometry (LC/MS-MS)
Therapeutic: 25−104 μg/mL; steady-state trough levels are dose proportional in adults. Multiple daily doses of 1200, 2400, and 3600 mg/day gave trough levels of 25−35, 47−63, and 62−104 μg/mL, respectively. Steady-state peak concentrations are dose proportional in children ages 4 to 12 years over a range of 15, 30, 45 mg/kg/day. The dose proportional peak concentrations were reported as 17, 32, and 49 μg/mL, respectively at two to six hours postdose. Co-administration of carbamazepine, phenytoin, phenobarbital, or primidone can cause a decrease in felbamate plasma concentrations; conversely, valproic acid can increase concentrations.1 In children, a similar effect was found with carbamazepine and phenytoin decreasing levels and an opposite effect with valproic acid.2
Following oral administration, felbamate is 25% bound to serum albumin. Approximately 40% to 50% of the absorbed dose appears unchanged in the urine. The rest is present as nonactive metabolites, including parahydroxyfelbamate, 2-hydroxyfelbamate, and felbamate monocarbamate. Felbamate has an elimination half-life of 20 to 23 hours. The apparent volume of distribution is 0.7−1.0 L/kg.
Serum or plasma
Transfer separated serum or plasma to a plastic transport tube.
Causes for Rejection
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|716530||Felbamate (Felbatol(R)), Serum||6899-9||716531||Felbamate, Serum||ug/mL||6899-9|