Liquid chromatographic assay with fluorescence detection to determine ajmaline in serum from patients with suspected Brugada syndrome

Ajmaline is a Sodium Channel blocking, class 1A anti-arrhythmic drug. It has gained renewed interest in the field of cardiology as a diagnostic agent to reveal the electrocardiographic characteristics in patients with suspected Brugada syndrome. We developed a simple and precise high-performance liquid chromatographic assay to determine ajmaline in serum of patients. The samples were pre-treated using protein precipitation with perchloric acid and the extract was injected into the chromatographic system. The system consisted of an end-capped octadecyl silica column with isocratic elution using perchloric acid in a water-acetonitrile mixture. Ajmaline was detected by fluorescence at 290 and 355 nm for excitation and emission, respectively. The assay was validated in a 21-5300 ng/ml concentration range, the lower limit of quantification was 25 ng/ml. Within day precisions were 1.3-3.9%, between day precisions 2-7% and accuracies were between 95 and 99% for the whole calibration range. The drug was shown to be chemically stable under all relevant conditions. This assay has been successfully applied to pharmacokinetic-pharmacodynamic evaluations of intravenous ajmaline administration to patients with suspected Brugada syndrome.