Comparison of HPLC and RIA methods applied to the quantification of amisulpride in human plasma

Quantification of amisulpride occurred up-till now using radioimmunoassay (RIA). A high performance liquid chromatographic (HPLC) assay with fluorimetric detection has been developed, which can be reproduced easily by any other laboratory. The aim of this paper is to compare amisulpride plasma levels (determined by RIA and HPLC) in 51 patients who received daily up to 800 mg of amisulpride in fractioned doses by IM or oral route, eventually together with other medications. Assay conditions and characteristics are briefly described and discussed. Results obtained with RIA and HPLC are compared and relative errors between both methods are calculated and examined as a function of the concentrations quantified. Correlation analysis using the concentrations (linear correlation) or their logarithm (logarithmic correlation) were realized for different concentration ranges. In fact, in the present case, logarithmic correlation was a more appropriate data processing method, which showed intercepts close to 0 and slopes close to 1. In conclusion, both methods are specific and sensitive enough to ensure the follow up of clinical studies. RIA may therefore be replaced whenever necessary by PHLC, without subsequent influence on the results.