From Lab to Upscale—Boosting Formulation Performance through In Vitro Technologies ^†

Pre-stability studies carried out throughout the development of a diclofenac emulgel formulation have shown a clear decrease in the drug release rate. In order to address the root-cause associated with this phenomena, product historical data were retrieved and analyzed following a retrospective Quality by Design (rQbD) approach. The quality target product profile (QTPP) was established, and risk assessment tools were used to identify the most relevant parameters affecting formulation performance. These consisted in (i) mixing time, (ii) sodium hydroxide content and (iii) carbopol grade. Following a 2³ full factorial design, the pH, viscosity, in vitro release rate and cumulative amount of drug released at the end of the release experiment were selected as responses to statistically model the available data. It was observed that higher sodium hydroxide concentrations induce a decrease in viscosity, consequently resulting in a superior pharmaceutical performance. Moreover, as a secondary effect, a lower carbopol viscosity yields lower release outputs. The estimated models were used to define a feasible working region, which was further confirmed at an industrial scale. This work highlights the use of rQbD principles to achieve a greater product understanding. By doing so, specific strategies can be applied to product manufacture in order to consistently meet QTPP requirements.