To investigate the feasibility of applying for bioequivalence exemption based on parallel artificial membrane permeability assay (PAMPA) data by evaluating the solubility and in vitro permeability of levofloxacin, comparing the prescription differences between the generic and reference formulations, assessing the impact of disparate excipients on the permeation behavior of the active pharmaceutical ingredient (API), and predicting the bioequivalence of the two formulations.

The dissolution of the raw material at pH 1.0 to pH 6.8 was determined using high-performance liquid chromatography. The μFlux^TM system was employed to determine the permeability of the raw material and the mixture of raw material with sodium stearyl fumarate in various media. pH 5.0 fed-state intestinal fluid, pH 6.5 fasted-state intestinal fluid, and pH 7.4 phosphate buffer (16 mL) were precisely added to the donor chamber, while 16 mL of Accepter Sink Buffer was added to the receptor chamber. The rotor speed was set at 200 r·min^-1, and the collection time was 180 min. Determine the permeability of the raw material and the mixture of raw material with sodium stearyl fumarate in various media, as well as the permeability of the raw material in the reference and generic formulations powders. The impact of newly added excipients and other changed excipients on API was evaluated through a two-tailed t-test. The Macro Flux^TM system was used to measure the dissolution-permeation curves of the reference and generic formulations, intestinal simulation fluids at pH 5.0 and pH 6.5 (1 000 mL) were added to the dissolution cup as dissolution media, with a stirring speed of 75 r·min^-1 using a paddle method, 12 mL of Accepter Sink Buffer was added to the receptor chamber, and the stirring speed of the micro-stirring rod was set at 450 r·min^-1, one tablet of each reference or generic formulation was placed in the dissolution cup, and the dissolution-permeation curves of the formulations were measured. The similarity of dissolution curves was compared, and the permeability rate (J_Flux) and cumulative drug permeation amount (AMT) were calculated to predict the bioequivalence of the two formulations, ensuring that the 90% confidence interval for the geometric mean ratio of J_Flux and AMT of the two formulations fell within the range of 80% to 125%.

Levofloxacin solubility ranged from 16.4 mg·mL^-1 to 62.7 mg·mL^-1 across different mediums, its permeability in pH 5.0 fed-state simulated intestinal fluid, pH 6.5 fasted-state simulated intestinal fluid, and pH 7.4 phosphate-buffered saline was 2.92×10^-6 cm·s^-1, 1.01×10^-5 cm·s^-1, and 1.07×10^-5 cm·s^-1, respectively. The addition of sodium stearyl fumarate showed no significant difference in permeability compared to the original API (P<0.05), and there were no significant differences between the powder API of the reference and generic formulations (P<0.05). The dissolution curves of both formulations were similar, with the 90% confidence interval for JFlux and AMT within the predefined range.

Levofloxacin tablets, classified as BCS Class Ⅰ, demonstrated that the altered excipients in the formulation did not impact on the API’s permeability, confirming bioequivalence between the reference and generic formulations. The bioequivalence exemption study based on PAMPA can be utilized for permeability studies of raw materials, excipient screening and optimization, and prediction of formulation bioequivalence, effectively reducing drug development costs and time. This study provides reference data for pharmaceutical companies applying for bioequivalence exemptions.