LC-MS-MS Simultaneous Determination of Paracetamol, Pseudoephedrine and Chlorpheniramine in Human Plasma: Application to a Pharmacokinetic Study

A liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma. Diphenhydramine was used as the internal standard. Analytes were extracted from alkalized human plasma by liquid-liquid extraction (LLE) using ethyl acetate. After electrospray ionization positive ion fragments were detected in the selected reaction monitoring (SRM) mode with a triple quadrupole tandem mass spectrometer. The method was linear in the concentration range of 20.0-10000.0 ng mL⁻¹ for paracetamol, 1.0-500.0 ng mL⁻¹ for pseudoephedrine and 0.1-50.0 ng mL⁻¹ for chlorpheniramine. The intra- and inter-day precisions were below 14.5% and the bias was between -7.3 and +2.8% for all analytes. The validated LC-MS-MS method was applied to a pharmacokinetic study in which each healthy Chinese volunteer received a tablet containing 300 mg benorylate, 30 mg pseudoephedrine hydrochloride and 2 mg chlorpheniramine maleate. This is the first assay method described for the simultaneous determination of paracetamol, pseudoephedrine and chlorpheniramine in human plasma samples.