Mixing

Abstract

Mixing is an important process in the pharmaceutical industry; it ensures the uniformity of composition among all components by blending them; it is a vital step to achieve dose uniformity. To achieve optimal mixing, factors such as particle size, density, and shape need to be considered, as these can affect the mixing process. The main forces driving the mixing process are convection, diffusion, and shear. The goal of mixing is to reach a state known as a perfect mixture, where the concentration gradient of the drug is zero across the entire mixture. However, this state is unattainable in practice and instead, an acceptable mixture where the concentration gradient is minimal is desired. The rate of mixing follows first-order kinetics. The common equipment used for mixing is a rotating shell blender with and without an agitator, and a stationary shell. Difficulty in achieving blend uniformity of low-dose active ingredients with other excipients is often observed, which could be resolved by using customized approaches. Scale-up is also a significant consideration, and trial-and-error or prior experience are the primary methods for achieving the desired outcome. Another approach, the Froude number method, is a mathematical model that has its own advantages and limitations in the scale-up of mixtures.