Sensitive determination of sulpiride in human plasma by high-performance liquid chromatography

We developed a simple, sensitive and reliable method for the determination of sulpiride, a specific antipsychotic drug, in human plasma using high-performance liquid chromatography. A structurally related benzamide, tiapride, was used as the internal standard. A Sep-Pak C₁₈ cartridge was used to extract a sample from 1 ml of plasma. The extract was dissolved in methylene chloride, and then back-extracted with 0.01 M hydrochloric acid. The aqueous layer was put on a octadecylsilica column with a mobile phase of 50% acetonitrile in 0.01 M phosphate buffer (pH 3.0). A fluorescence detector with excitation at 300 nm and emission at 365 nm was used for detection. The calibration curve was linear in the concentration range of 10-1500 ng/ml, and the lower limit of detection was 1 ng/ml. We used this method to examine plasma levels of sulpiride in 14 inpatients being treated with sulpiride for 6 months. The determined plasma levels were 70.1-1121.2 ng/ml, and the correlation between daily dose and plasma concentration was positive. This simple, reliable method is expected to be put to good use in forensic and hospital laboratories.