Development and Validation of a Discriminating Dissolution Method for Darifenacin Extended-Release Tablets

A dissolution test for darifenacin 15-mg extended-release tablets was developed and validated according to current FDA and USP guidelines. The sink condition was evaluated, and a 24–1 factorial design was employed for method development. In vivo data were obtained from the literature, and the fraction and percentage of dose absorbed (FA) was calculated using the Wagner–Nelson method. The best dissolution conditions were achieved using USP Apparatus 1 (basket) with 900 mL of dissolution medium containing 2% SDS at 50 rpm. A successful linear regression model of fraction of drug absorbed versus dissolved was achieved (R2 = 0.9997, p < 0.05). The best fit for drug release kinetics was provided by the Korsmeyer–Peppas model. The validation was performed with an HPLC–UV method, and results for specificity, linearity, precision, and accuracy were in accordance with guidelines. The proposed method achieved a Level A correlation with the fraction of dose absorbed. Additionally, the discriminatory power of the method was challenged. The results show that the proposed test is adequate to evaluate the in vitro profile for extended-release darifenacin tablets.