Quantification of typical antipsychotics in human plasma by ultra-high performance liquid chromatography tandem mass spectrometry for therapeutic drug monitoring

A selective and sensitive method was developed for the simultaneous quantification of seven typical antipsychotic drugs (cis-chlorprothixene, flupentixol, haloperidol, levomepromazine, pipamperone, promazine and zuclopenthixol) in human plasma. Ultra-high performance liquid chromatography (UHPLC) was used for complete separation of the compounds in less than 4.5 min on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm; 1.7 μm), with a gradient elution of ammonium formate buffer pH 4.0 and acetonitrile at a flow rate of 400 μl/min. Detection was performed on a tandem quadrupole mass spectrometer (MS/MS) equipped with an electrospray ionization interface. A simple protein precipitation procedure with acetonitrile was used for sample preparation. Thanks to the use of stable isotope-labeled internal standards for all analytes, internal standard-normalized matrix effects were in the range of 92-108%. The method was fully validated to cover large concentration ranges of 0.2-90 ng/ml for haloperidol, 0.5-90 ng/ml for flupentixol, 1-450 ng/ml for levomepromazine, promazine and zuclopenthixol and 2-900 ng/ml for cis-chlorprothixene and pipamperone. Trueness (89.1-114.8%), repeatability (1.8-9.9%), intermediate precision (1.9-16.3%) and accuracy profiles (<30%) were in accordance with the latest international recommendations. The method was successfully used in our laboratory for routine quantification of more than 500 patient plasma samples for therapeutic drug monitoring. To the best of our knowledge, this is the first UHPLC-MS/MS method for the quantification of the studied drugs with a sample preparation based on protein precipitation.