A validated HPLC-ESI-MS method for the determination of loratadine in human plasma and its application to pharmacokinetic studies.

A liquid chromatographic-mass spectrometric (LC-MS) assay was developed and validated for the determination of loratadine in human plasma using reversed-phase HPLC combined with electrospray ionization (ESI) mass spectrometry. The analysis involved a simple liquid-liquid extraction. The organic extract was then evaporated and the residue was reconstituted in mobile phase. The reconstituted solution was injected into an HPLC system and was subjected to reverse-phase HPLC on a 5-microm ODS-3 column at a flow-rate of 0.2 ml/min. The mobile phase comprised of acetonitrile-ammonium acetate (pH 4.0; 0.02 M, using formic acid to adjust) using gradient elution. Loratadine was detected in the single ion monitoring (SIM) mode. Standard curves were linear over the concentration range of 0.2-100 ng/ml. The mean predicted concentrations of the quality control (QC) samples deviated by less than 10% from the corresponding nominal values; the intra-assay and inter-assay precision of the assay were within 12% relative standard deviation. The extraction recovery of loratadine was more than 80%. The validated assay was applied to a pharmacokinetic study of loratadine in human plasma following the administration of a single loratadine tablet (40 mg).