Development of a highly sensitive LC–MS/MS method for simultaneous determination of rupatadine and its two active metabolites in human plasma: Application to a clinical pharmacokinetic study

•An assay method of rupatadine with two metabolites in human plasma was developed.•First report to investigate the back-conversion of two metabolites of rupatadine.•LLOQ between 0.035–0.05 ng/mL for rupatadine and its metabolites was obtained.•First report comparing PK profile between single and multiple doses of rupatadine.•First report comparing PK profile between male and female dosed with rupatadine.

An easy LC–ESI–MS/MS method was developed and validated for simultaneous determination of rupatadine (RT) and its two active metabolites, namely desloratadine (DT) and 3-hydroxydesloratadine (3-OH-DT), in human plasma. The chromatographic separation was carried out on a C18 column with gradient elution by using methanol and 10 mM ammonium acetate containing 0.1% (v/v) formic acid. The lower limit of quantification (LLOQ) was 0.05, 0.035 and 0.035 ng/mL for RT, DT and 3-OH-DT, respectively. The intra- and inter-day precision of analytes were within the range of 1.0–4.7% and 2.2–12.1%, respectively. The intra- and inter-day accuracy of analytes were within the range of −7.7% to 5.2% and −4.1% to 4.8%, respectively. The method was successfully applied to a pharmacokinetic study of RT and its two metabolite DT and 3-OH-DT in healthy volunteers following single (10, 20, 40 mg) and multiple (10 mg) oral doses of rupatadine fumarate tablets.

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