OBJECTIVE To establish an in vitro release test( IVRT ) evaluation method for loxoprofen sodium cataplasms, and to investigate the consistency of release behavior between test preparation from different manufacturers and the reference preparation.

METHODS Avertical modified Franz diffusion cell was used with a 0.45 µm polyethersulfone membrane as the artificial membrane. The receiving medium was 12 mL of degassed pH 6.8 phosphate buffer, with a stirring speed of 500 r·min⁻¹ and a temperature of 32 ℃. Samples of 12 mL were collected at 0.5, 1, 2, 3, 4, 5, 6, 8, 10, and 12 h, with immediate replenishment of the receiving medium. The release profile of the drug over time was determined by HPLC. The consistency of in vitro release between the test and reference preparations was evaluated using the model-independent similarity factor(f₂) and the non-parametric Mann-Whitney U test.

RESULTS The f₂ factors for the three test preparations compared with the reference preparation were 83.08, 84.95, and 82.00, respectively. The 90% confidence intervals for the ratios of in vitro release rates were 95.21%−105.96%, 90.34%−96.41%, and 91.09%−97.63%, all within the acceptable range of 90%−111%, meeting the requirements of the Center for Drug Evaluation(CDE).

CONCLUSION The in vitro release behaviors of the three test preparations and the reference preparation were generally consistent. The established method can serve as a reference for the consistency evaluation of generic loxoprofen sodium cataplasms.