Abstract: A new HPLC MS method to determine loratadine in human plasma was established. The method involved extracting drug with organic solvent under basic conditions. The samples were seperated by ODS column and determined by mass detector. The calibration curve of loratadine was linear within the range of 0.4~100 ng·mL^-1 with r = 0.9995. The recovery of this method was within 95%~104%, within day and between day RSD were less than 12%. To study the pharmacokinetics and relative bioavailability of loratadine tablets, two formulations of loratadine tablets were given to 18 healthy male volunteers according to a randomized 2 way cross over design. The Cmax, AUC0-t and Tmax values of the two formulations were 51.89±20.18 ng·mL^-1 and 52.48±22.35 ng·mL^-1; 140.75±88.42 ng·h·mL^-1 and 147.24±92.33 ng·h·mL^-1; 0.81±0.35 h and 0.81±0.27 h respectively. Results from statistic analysis showed that there were no significant difference between the Cmax, AUC0-t and Tmax values of the two formulations. The relative bioavailability of tablets I with respect to tablets II was 97%±13% from the AUC0-t measurement. Bioequivalance was observed between the two tablets.

Key words: Loratadine, Loratadine, HPLC MS, HPLC MS, Pharmacokinetics, Pharmacokinetics, Bioavailability, Bioavailability