Drug monitoring and toxicology: a simple procedure for the monitoring of felbamate by HPLC-UV detection

This article describes a simple isocratic high-performance liquid chromatographic (HPLC) method with UV detection for the determination of felbamate in the serum of patients with epilepsy. Sample preparation requires only protein precipitation with a single-step methanol extraction. After centrifugation, the resulting supernatant was injected directly onto the HPLC system. Separation was achieved by reversed-phase HPLC, using a 5-microm Microsorb-MV C(18) column (250 x 4.6 mm) connected to a Silica C(18) guard column (20 x 4.6 mm) and a mobile phase consisting of a mixture of phosphate buffer (pH = 6.9, 0.05 M), methanol, and acetonitrile (64:18:18, v/v/v). The flow rate was at 1.0 mL/min and column temperature was set at 35 degrees C. Quantitation was performed by measurement of the UV absorbance at a wavelength of 210 nm. Calibration curves were linear over a range of 2-200 mg/L, which covered the proposed range of 50-150 mg/L for reference. Both within-run and between-run precision were lower than 5%. Recoveries ranged between 97% and 105% for spiked and pooled samples. No interferences with other common antiepileptic drugs (except zonisamide) were observed. The method requires only 100 microL of serum or less. It is simple and fast (sample preparation and analysis time) and suitable for routine clinical use.