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.