Simultaneous determination of centbutindole and its hydroxy metabolite in serum by high-performance liquid chromatography.

A high-performance liquid chromatographic assay has been developed and validated for the determination of centbutindole and its hydroxy metabolite in serum. The method involves extraction of serum samples with diethyl ether at pH greater than 8, back-extraction into 0.5 M hydrochloric acid and finally again with diethyl ether after addition of 2 M potassium hydroxide. Separation was accomplished by reversed-phase high-performance liquid chromatography on a cyano column with an acetonitrile-phosphate buffer system. The recovery of centbutindole and its metabolite was always greater than 80%. Calibration curves were linear over the concentration range 0.25-5 ng/ml for centbutindole and 0.05-1 ng/ml for the hydroxy metabolite. Although the lower limit of detection was 0.1 ng/ml for centbuntindole and 0.02 ng/ml for the hydroxy metabolite, the reliable limits of quantitation were 0.25 and 0.05 ng/ml, respectively, using 4 ml of serum.