Determination of amezinium in plasma by RP HPLC and its application to bioequivalence studies

A modified method is described for the determination of 4-amino-6-methoxy-l-phenylpyridazinium methyl sulfate (amezinium metisulfate) in plasma and in the dosage form. The method involves a sample preparation using SPE and liquid-liquid extraction and subsequent determination by high performance liquid chromatography. Retention time for amezinium was 3.2 min and there was no interference from plasma or amezinium metabolites. The method was applied for the drug determination during comparative studies of two different tablet formulation of amezinium.