Kaifeng Pharmaceutical (Group) Co., Ltd.

Primary Objective: To conduct a bioequivalence study of doxycycline hydrochloride tablets (test formulation, 0.1 g/tablet) manufactured by Kaifeng Pharmaceutical (Group) Co., Ltd. and Pfizer Japan Inc.'s certified doxycycline hydrochloride tablets (Vibramycin, reference formulation, 100 mg/tablet) in healthy Chinese subjects. The bioequivalence of the two formulations was compared after single administration under fasting and fed conditions. Secondary Objective: To evaluate the safety of single oral doses of the test formulation (doxycycline hydrochloride tablets, T) and the reference formulation (Vibramycin, R) in healthy Chinese adult subjects.

Main purpose: To investigate the pharmacokinetic parameters and relative bioavailability of doxycycline hydrochloride tablets (test preparation, 0.1 g/tablet) produced by Kaifeng Pharmaceutical (Group) Co., Ltd. and doxycycline hydrochloride tablets (Vibramycin, reference preparation, 100 mg/tablet) certified by Pfizer Japan Inc. using healthy Chinese subjects as subjects, to preliminarily evaluate the bioequivalence of the two preparations, and to assess their intra-individual variation and optimize the sampling time, so as to provide a reference for formal trials. Secondary purpose: To observe the safety of the test preparation and the reference preparation after administration in healthy subjects.