Bioequivalence Study of Two Olopatadine Hydrochloride Tablets in Chinese Healthy Subjects Under Fasting and Fed Conditions.

Olopatadine hydrochloride, a second-generation selective histamine H1 receptor antagonist, is an effective anti-allergic agent. This study evaluated the pharmacokinetics and bioequivalence of two olopatadine hydrochloride tablet formulations in healthy Chinese subjects under fasting (n = 24) and fed (n = 24) conditions. A single-center, randomized, open-label, single-dose, two-way crossover study was conducted, in which 48 subjects were randomized to receive 5 mg of the test or reference formulation, followed by a 7-day washout period. Blood samples were collected at predefined intervals up to 24 h post-dose, and olopatadine plasma concentrations were measured using a validated liquid chromatography-tandem mass spectrometry method. The results demonstrated no significant differences in the pharmacokinetic profiles between the test and reference formulations under fasting or fed conditions. The 90% confidence intervals (CIs) for the ratio of geometric means of Cmax, AUC0-t, and AUC0-∞ of olopatadine hydrochloride under both conditions were within the bioequivalence range of 0.80-1.25. A high-fat diet delayed olopatadine hydrochloride absorption, leading to a reduction in Cmax to approximately 60% of the fasting value and a decrease in AUC to 85%-90%. No serious adverse events occurred, and safety profiles were comparable between formulations. This research confirmed the bioequivalence and similar safety of the generic olopatadine hydrochloride tablets to the reference formulation.