An HPLC/UV method for the determination of RGH-1756 in dog and rat plasma

RGH-1756 (1-(2-methoxy-phenyl)-4-{4-[4-(6-imidazo[2,1-b]-thiazolyl)-phenoxy]-butyl}-piperazine dimethansulphonate) is a novel atypical antipsychotic candidate of Gedeon Richter Ltd. A new HPLC method has been developed and validated for the quantitative determination of RGH-1756 in dog and rat plasma. The compound and the internal standard are extracted from the biological samples by a simple and fast liquid–liquid extraction method, using 1-chlorobutane. The recovery for RGH-1756 is about 90%. The extracts are analyzed by reversed phase HPLC (column: Supelcosil-LC-18-DB 250*4.6 mm, 5 μm, eluent:acetonitrile:methanol:0.2 molar ammonium-acetate 40:25:35, λ=254 nm). The assay is specific for RGH-1756. The standard curves are linear in the range between 10 and 2000 ng ml −1. The overall precision (expressed as CV%) and accuracy (expressed as bias%) of quality controls and calibration standards are within 15%. The validated lower limit of quantification is 10 ng/ml. No indications have been found for possible instabilities of RGH-1756 in plasma, in the extraction solvent, or after repeated thawing-freezing cycles. The method has been succesfully applied for the bioavailability studies of RGH-1756 in the two animal species. In these studies results of the inprocess method validation have shown the reliability of the method, too. CV% of quality controls in the rat study has been found between 7.4 and 10.0%, in the dog study between 4.1 and 12.5%. The bias has ranged from 0.4 to 3.8% and from −4.5 to 1.2% in the rat and dog study, respectively.