To establish an in vitro permeation method for crisaborole ointment and to provide a reference for the bioequivalence of crisaborole ointment.

The HPLC method was used to determine the permeability of crisaborole ointment, and the vertical Franz diffusion pool method was used to study the release characteristics of the ointment in vitro. The chromatographic column was Thermo BDS Hypersil-C₁₈(150 mm×4.6 mm, 5 μm), with 0.1% phosphoric acid solution-acetonitrile (60：40) as the mobile phase, flow rate of 1.5 mL·min^-1, column temperature of 30 ℃, detection wavelength of 254 nm, and injection volume of 10 μL.

The peak shape of crisaborole in the chromatogram of the test sample was good. There was no peak at the position of crisaborole in the negative sample chromatogram, which did not interfere with the determination. The linear relationship of crisaborole was good within the range of 0.026-21.02 μg·mL^-1 (r≥0.999). In six repeated experiments, the mean maximum transmittance (J_max) of the self-made product and the reference formulation were compared (odds ratio: 0.94). Simultaneously calculate the confidence interval for J_max, with a 90% confidence interval ranging from 87.9% to 102.0%. The mass conservation percentage of each sample was 94.1%-101.1%(n=12). The reference solution was left at room temperature for 26 h, with a peak area RSD of 0.44%. The self-made product and reference preparation were left in a water bath at room temperature and 32 ℃ for 26 h, with peak area RSD ranging from 0.78% to 1.1%, indicating good stability of the solution. For the three batches of samples tested, the ratio of the mean J_max values of the self-made product and the reference formulation was within the range of 0.92-0.97. Simultaneously calculate the confidence interval for J_max, with a 90% confidence interval ranging from 84.8%-100.7%.

This method is simple and convenient to operate, with high selectivity, strong exclusivity and high accuracy.