A Simple and Rapid HPLC-UV Method for the Determination of Retigabine in Human Plasma.

A simple and rapid high-performance liquid chromatographic method with ultraviolet detection was developed for the quantitative determination of retigabine, known also as ezogabine, in human plasma. The assay uses a simple solid-phase extraction for sample preparation and direct injection of the extract into the chromatograph. Flupirtine is used as an internal standard. Chromatographic separation is achieved on a C-18 Chromolith column (Chromolith Performance, 100 x 4.6mm i.d.), using as mobile phase water/acetonitrile/methanol (72:18:10v/v/v) mixed with 0.1% of 85% phosphoric acid. Isocratic elution is conducted at a flow rate of 1.5mL min(-1). The total duration of a chromatographic run is 7min. Calibration curves are linear over the 25-2000ng mL(-1) concentration range, with a limit of quantitation of 25ng mL(-1). Other performance characteristics include high precision (intra- and inter-day coefficients of variation 12.6%) and high accuracy (99.7%-108.7%). The method is suitable for the investigation of concentration-response relationships in patients receiving therapeutic doses of retigabine.