The dimension or particle size uniformity of solid active pharmaceutical ingredients (APIs) and excipients are also critical parameters in the production of highly safe and efficient final drug dosage forms. This can be achieved through the process of milling, which is a critical unit operation that controls the particle size uniformity of a pharmaceutical drug product and therefore helps produce free-flowing powders.
Particle size reduction is also called comminution, and generally it is carried out to promote the efficient processing of solid particles by facilitating powder mixing (production of suspensions).
Some special functions of size reduction includes: exposing cells in plant tissue prior to API extraction; or reducing the bulk volume of a material to improve transportation efficiency.
It must be noted that in particle size uniformity, using different mills can give rise to different end-products from the same starting material, such that they would differ in the particle shape and proportion of fines in the final dosage form.
Advantages of Milling Process:
Prior to milling, the physical properties of API and its excipients must be reviewed for possible hazards involving high OEL levels, volatility, and explosion properties, as these will help in designing the most suitable milling equipment and possible barrier technology for the process.