Determination of felbamate concentration in pediatric samples by high-performance liquid chromatography

A simple and rapid procedure to determine felbamate (2-phenyl-1,3-propanedicl dicarbamate) concentrations in human plasma/serum by highperformance liquid chromatography is described. The method employs a highperformance liquid chromatography unit equipped with a C18 reverse-phase cartridge (3-mu l particle diameter, 3.2 x 40 mm), an acetonitrile/water gradient, and detection at 210 nm. The sample is deproteinized with acetonitrile containing internal standard (2-methyl-2-phenyl-1,3-propanediol dicarbamate), and the resulting supernatant, after diluting 1:1 with water, is injected onto the column. The felbamate and internal standard are eluted with a linear gradient of 0% to 22% acetonitrile for 11 minutes at a flow rate of 0.8 ml/minute. Under these conditions, felbamate and the internal standard are eluted at 9.2 +/- 0.03 and 10.8 +/- 0.03 minutes, respectively. The assay is linear from 10 to 400 mu g/ml. It is highly reproducible; at 100 mu g/ml felbamate, within-day and between-day coefficients of variation are less than 0.5% and 4.3%, respectively. Recovery is greater than or equal to 95%. No interferences from other common antiepileptic drugs and analgesics are observed. Advantages of this method include simple and fast sample preparation; use of a gradient to eliminate interferences; and use of a cartridge column, which is economical, provides good resolution, allows rapid equilibration and elution, and operates at low back pressures. The method requires samples of only 100 mu l and is ideal for pediatric samples.