IVRT and IVPT of Desonide Lotion and Cream: Correlation with Human Bioequivalence Study

Background

Topical bioequivalence (BE) studies are critical for approving affordable generic formulations while ensuring safety and efficacy comparable to branded products. However, traditional clinical endpoint studies for topical formulations are costly, time-consuming, and complex. This study explores an in vitro release testing (IVRT) and an in vitro permeation testing (IVPT). The formulations were further evaluated in a bioequivalence study to establish therapeutic equivalence.

Methods

The IVRT method was developed and validated using 50% ethanol in pH 4.0 acetate buffer as the receptor medium and a Nylon 66 synthetic membrane, demonstrating linearity, precision, sensitivity, and robustness. The IVPT method utilized porcine skin as a substitute model for human skin and saline solution as receptor media to achieve comparable cumulative permeability and penetration rates between test and reference formulations. The pilot and pivotal skin blanching assay was performed using 18 and 100 subjects, respectively.

Results

The 90% confidence interval of test and reference formulation for the IVRT was 97.78%~107.1% for lotion and 93.5 ~ 112.8% for cream (75%~133.33%). The test and reference formulation of cream and lotion reached the maximum permeability rate (Jmax) at 24 h, and the T/R ratio was 100.0% for cream and 110.0% for lotion (90% CI with 80–125%0). The T/R ratio of the cumulative permeability for the cream and lotion formulation was 95.2% and 104.5% respectively. The average recoveries after the permeation test for T and R cream formulations were 97.4 ± 7.7% and 101.6 ± 10.5% and for lotion, 88.2 ± 5.1 and 86.8 ± 3.9 respectively. Both IVRT and IVPT results confirmed bioequivalence. Additionally, a skin blanching assay further validated the bioequivalence of the test formulations.

Conclusion

The findings demonstrate that both formulations exhibit comparable release and permeation characteristics, supporting their bioequivalence in human subjects. This integrated approach highlights the utility of IVRT and IVPT as robust tools for formulation development and in vitro bioequivalence assessment of topical dermatological products.