Simultaneous determination of iloperidone and its two active metabolites in human plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study.

A selective, sensitive and accurate high-performance liquid chromatographic- tandem mass spectrometry (HPLC-MS/MS) method for simultaneous determination of iloperidone and its two active metabolites, P88 and P95, in human plasma has been first developed and validated. The analytes and internal standard (IS), pioglitazone hydrochloride, were extracted from human plasma via liquid-liquid extraction with ethyl acetate and separated on a CAPCELL PAK C18 MG IIIcolumn (150mm×2.0mm, 5μm) set at 40°C. The mobile phase was acetonitrile: 5mM ammonium formate containing 0.3% formic acid (pH 4.8) (25:75, v/v), with a flow rate of 0.35mL/min. The mass spectrometer was operated in multiple reaction monitoring (MRM) mode using the transitions m/z 427.2→261.2 for iloperidone, m/z 429.1→261.1 for P88 and P95, and m/z 357.1→133.7 for the I.S. (pioglitazone hydrochloride). The method was validated to be linear over the concentration range of 10-10,000pg/mL for iloperidone and P88, 50-15,000pg/mL for P95. The mean recoveries were more than 78.88%, and the intra- and inter-day precisions were less than 10.24% and accuracy was -5.78 to 5.40%, which indicated that the quantitative method was reliable and accurate. The validated method has been successfully applied to a human pharmacokinetic study of iloperidone and two active metabolites, P88 and P95, after oral administration of 4mg iloperidone tablets in 12 healthy Chinese volunteers.