Enzyme immunoassay for flecainide.
In order to develop an enzyme immunoassay (ELISA) for measurement of plasma flecainide levels, we first synthesized flecainide-hemisuccinate-BSA as immunogen. A highly specific antiserum was then raised in rabbits. Enzyme-labelled flecainide was prepared by the mixed anhydride method using hemifumarate-flecainide and horse radish peroxidase. The limit of detection was 10 ng/ml, the method was linear up to 1,000 micrograms/l. The intra and inter-assay variation was 5.1-7.8%. Cross reactivity with various metabolites of flecainide or some chemically related drugs was less than 0.1%. By contrast the cross reaction with some structural analogues achieved 25%. The importance of parts of the aromatic ring structure in immunogenic properties of this drug is discussed.