Application of a bonded-phase extraction column for rapid sample preparation of flecainide from human plasma for high-performance liquid chromatographic analysis--fluorescence or ultraviolet detection.

A simple, rapid, selective, and sensitive procedure for the monitoring of flecainide levels in human plasma is described. The drug and the internal standard--a positional isomer of flecainide--are separated from plasma by the use of a disposable extraction column packed with reversed-phase sorbent. The drug and internal standard which are selectively retained on the extraction column are eluted. An aliquot is injected onto a mu-Bondapak phenyl column and eluted with a mixture of acetonitrile and 0.06% phosphoric acid (40:60, vol/vol) at a flow rate of 2 ml/min. The eluted drug and internal standard are measured by a fluorescence detector with excitation and emission wavelengths of 300 and 370 nm, respectively. The linear range is 3-2,000 ng/ml, and the sensitivity limit is 3 ng/ml with 1 ml of plasma. The within-day coefficient of variation was 1.1-4.6% at concentrations ranging from 3 to 1,600 ng/ml. Many drugs given concomitantly with flecainide acetate do not interfere with the assay. The method compares favorably to a well-documented gas-liquid chromatographic method and is suitable for use in plasma drug level monitoring for patient management as well as in pharmacokinetic studies. Similar results were obtained using an alternate detection method (ultraviolet detection at 298 nm).