A selective HPLC method for the determination of indapamide in human whole blood: Application to a bioequivalence study in Chinese volunteers

Indapamide was extracted from human whole blood with diethyl ether and was determined by a HPLC-UV method using an Inertsil ODS-3 column and an isocratic mobile phase consisting of 55% buffer solution (2 g KH2PO4, 3 ml H3PO4 and 3.5 ml triethylamine in 1 l of H2O), 40% acetonitrile and 5% methanol for 12.5 min, and then a gradient flush from 100% isocratic to a mixture of 20% isocratic mobile phase and 80% methanol for 3 min. Indapamide and glipizide (internal standard) were eluted from the column at about 10.5 and 12.8 min, respectively. The method had within day precision values in the range ±1.2 to ±9.7% (n = 5) and between day precision in the range ±3.3 to ±9.7%. The method was linear over the range of 10–400 ng/ml of indapamide in blood (R = 0.999). The LOQ (s/n = 10) of the method was 10 ng/ml. The method was applied in a study of the pharmacokinetics and bioequivalence of generic indapamide capsules (2.5 mg) in comparison with reference indapamide tablets (2.5 mg), in 20 healthy male Chinese volunteers. The mean values of major pharmacokinetic parameters of Cmax, AUC0–48, AUC0–∞, Tmax, and t1/2 of indapamide in healthy male Chinese volunteers after po a single 5 mg dose for the test product were 331.0 ± 39.2 ng/ml, 6193.7 ± 873.5 ng h/ml, 7311.8 ± 1232.3 ng h/ml, 3.2 ± 0.9 h, and 17.3 ± 2.8 h, respectively. There was no significant differences between the two formulations.