Selective determination of sultopride in human plasma using high-performance liquid chromatography with ultraviolet detection and particle beam mass spectrometry.

We developed a sensitive and selective method for determining levels of sultopride, a neuroleptic drug of the substituted benzamide, in human plasma using high-performance liquid chromatography (HPLC) combined with UV detection and particle beam mass spectrometry (PBMS). Sultopride was extracted with tert.-butylmethyl ether using a salting-out technique. Tiapride served as an internal standard (I.S.). Sultopride and I.S. were separated by HPLC on a silica column with a mobile phase of acetonitrile-0.1 M ammonium acetate (94:6, v/v). The calibration curves were linear over the concentration range from 5 to 1000 ng/ml by HPLC with UV detection and from 10 to 1000 ng/ml with PBMS detection. The limit of quantitation was 5 ng/ml with UV detection and 10 ng/ml with PBMS detection. The absolute recovery was 92% and the within-day coefficients of variation were 2.9-7.1% at plasma concentrations from 50 to 500 ng/ml, determined by HPLC with UV detection. Using this method, we measured the plasma concentrations of sultopride with replicate analyses in four hospitalized patients and steady-state plasma levels were determined to be 161.6 +/- 30.8, 321.1 +/- 93.7, 726.5 +/- 143.1 and 1273.6 +/- 211.2 ng/ml, respectively.