SIMULTANEOUS DETERMINATION OF A NOVEL ANTIARRHYTHMIC AGENT, 7-BENZYL-3-THIA-7-AZABICYCLO[3.3.1] NONANE AND ITS SULFOXIDATION METABOLITE IN PLASMA AND URINE BY HPLC

A HPLC method was developed for the simultaneous determination of the concentrations of 7-benzyl-3-thia-7-azabicyclo[3.3.1]nonane (I) as the hydrochloride and the corresponding sulfoxide (II), the major metabolite, in dog plasma and urine. Plasma and urine samples were alkalinized and extracted with chloroform. An aliquot was injected on to a HPLC system with a C6 reversed-phase column and an UV detector. Acetonitrile-methanol-37.5 mM phosphate buffer, pH 6.8 (28:28:44 v/v) containing 4.0 mM triethylamine was used as a mobile phase. The compounds I and II were detected at 261 nm. The extraction recovery for I and II was 85% and 94% from plasma and 89% and 91% from urine, respectively. Good linearity (r>0.994) was observed throughout the range of 0.1-10.0 mu g/ml for I and 0.04-10 mu g/ml for II in plasma and in urine. Intra- and inter-assay variabilities were less than 8%. The accuracy of this method was > 95% for both compounds, and the limits of quantitation were 0.08 mu g/ml for I and 0.03 mu g/ml for II in plasma, and in urine, respectively. This method was applied to determine plasma and urine concentrations of I and II simultaneously in a dog treated with I.