ABSTRACT
A simple and rapid reverse phase high-performance liquid chromatographic [RP-HPLC] method with UV detection has been described for the determination of lansoprazole in human serum. Carbamazepine was used as internal standard. The drug and the internal standard in serum were extracted twice with diethyl ether, followed by evaporation, reconstitution in the mobile phase and injection into the chromatographic system. The method utilized a Nova-Pak CI8 4-micro m column [150x3.9 mm i.d.] together with an isocratic mobile phase consisted of 0.02M sodium dihydrogenphosphate- acetonitrile- methanol [58: 23: 19%, v/v/v]. The mobile phase was adjusted to pH 7.3 with 5M NaOH and pumped at a flow rate of 1.8 mI/min. The UV detector was set at 285 Rm. Running time per single analysis was less than four minutes. The response of the assay was linear with a correlation coefficient, r = 0.9993. The within and between-day coefficients of variation for three different concentrations [50-1500 ng/ml] ranged from 1.14 to 8.26% and from 1.66 to 8.02%, respectively. The average recovery of the concentration range stated was better than 96.5%. Stability testing revealed that lansoprazole was stable in serum at -20°C for two weeks. The method was successfully applied in a bioassay study of two products each in the form of enteric-coated granules in capsules containing 30 mg lansoprazole, administered orally to eighteen healthy male volunteers