[Determination of the concentration of a new antiarrhythmic, flecainide, in plasma using high pressure liquid chromatography (HPLC): sample preparation with extraction columns].

A method is described for the rapid determination of flecainid (Tambocor) in human plasma. Flecainid is removed from alkalized plasma by binding to a C-18 extraction column. After washing the column with methanol/water (1 + 1, by vol.) and acetonitrile/water (45 + 55, by vol.), the drug is extracted with methanol and determined by HPLC. Sample preparation takes about 15 minutes. With this method, flecainid can be determined directly in the concentration range 100-2000 micrograms/l, with an accuracy of 5-10% depending on the concentration. The results agree well with those obtained by the longer established but lengthy liquid extraction method.