Supplementary Material for: Kinetic Monitoring of IVRT using UV-Vis Spectrophotometry with Hydrocortisone Creams

Introduction A new method for conducting in-vitro release testing (IVRT) was developed by adapting Higuchi’s square root approximation for use with UV-Vis spectrophotometry, and over the counter hydrocortisone formulations at 0.5% and 1.0% concentrations. This IVRT method was investigated for the required validation elements as specified by abbreviated new drug applications (ANDAs) and USP General Chapter for linearity and range, precision and reproducibility, and discrimination sensitivity, specificity, and selectivity. Methods IVRT kinetic experiments were conducted using UV-Vis spectrophotometer, a quartz cuvette, with measurements collected every 15 seconds for 5 minutes, and methanol as the receptor solution. Six measurements of the 1% hydrocortisone formulation were conducted over three different days, for a total of 18 measurements. The 0.5% formulation was measured six times over one day. Release rates were obtained by plotting the slope of Abs242 vs √t. HPLC was used to demonstrate specificity via an alternate analytical technique and to show membrane inertness. Results The hydrocortisone cream formulations demonstrated specificity via HPLC compared to a USP traceable hydrocortisone reference standard. IVRT sensitivity and selectivity were demonstrated by the statistically different release rates (slopes) of the 0.5% vs the 1% hydrocortisone formulations at 90% confidence interval (75-133.33%). Linearity throughout the duration of the assay was demonstrated through a r2 value of ≥0.97 for each experiment and for each formulation. All intra-run and inter-run precision calculations relating to the IVRT experiments had %CV values of ≤15%. Conclusion IVRT experiments were conducted using UV-Vis spectrophotometry kinetic monitoring of 0.5% and 1% hydrocortisone formulations. This IVRT method was validated for specificity, selectivity, sensitivity, linearity and range, precision and reproducibility following the guidance for ANDAs and USP General Chapter , thus demonstrating the capability of UV-Vis spectrophotometry as a reliable way of discerning release rates of semi-solid formulations. This novel approach can be conducted in a matter of minutes as opposed to hours, a vast improvement over conventional IVRT studies.