Abstract: AIM: To compare the bioavailability of norfloxacin tablets produced by Zhejiang Pharmaceutical Co., Ltd with the original product BACCIDAL, and to evaluate bioequivalence of two formulations, a randomized, open, two-cycle, self-crossing trial in healthy Chinese population was designed.  METHODS: Under fasting and fed conditions, healthy volunteers were given a single dose of norfloxacin test or reference tablets for 100 mg. Liquid chromatography-mass spectrometry (LC-MS/MS) method were used to determine drug concentration in the plasma taken at different time points before and after dosing. Pharmacokinetic parameters and the bioequivalence of the two formulations were calculated by WinNonlin 7.0 software. RESULTS: A total of 28 healthy volunteers were enrolled and completed the fasting test. The pharmacokinetic parameters for test and reference preparations in fasting state were as follows: Cmax were (607.62±125.24) ng/mL and (552.01±134.11) ng/mL; AUC0-t were (2 551.66±509.08) ng·mL-1·h and (2 429.98±460.47) ng·mL-1·h; AUC0-∞ were (2 675.40±523.04) and (2 557.68±485.43) ng·mL-1·h, t1/2  were (6.07±0.69) and (6.18±0.92) h. The 90% confidence intervals of the geometric mean ratio of Cmax, AUC0-t and AUC0-∞ for the test and reference preparations of norfloxacin tablets taken by healthy volunteers under fasting condition were 101.45%-121.94%, 98.96%-111.27% and 98.82%-110.76%. The pharmacokinetic parameters for test and reference preparations in fed state were as follows: Cmax were (256.54±58.87) and (300.80±94.67) ng/mL; AUC0-t were (1 314.74±349.92) and (1 278.60±314.77) ng·mL-1·h; AUC0-∞ were (1 413.73±361.98) and (1 374.98±321.62) ng·mL-1·h, t1/2 were (6.66±1.23) and (6.66±1.34) h. The 90% confidence intervals of the geometric mean ratio of Cmax, AUC0-t and AUC0-∞ for the test and reference preparations of norfloxacin tablets taken by healthy volunteers under fed condition were 81.42%-93.56%, 99.61%-105.58% and 99.80%-105.21%. CONCLUSION: The test preparation of norfloxacin tablets and the reference preparation are bioequivalent, and they can be used interchangeably clinically. 

Key words: norfloxacin, bioequivalence, pharmacokinetics, LC-MS/MS