Micronization

Micronization is a size-reduction process that produces particles in the micrometer range, commonly 1–100 micrometers. Reducing particle size increases surface area, which can enhance dissolution rate, bioavailability, flow properties, and content uniformity of solid formulations. The technique is widely used in pharmaceuticals to improve the oral absorption of poorly soluble drugs, and it also finds application in cosmetics, nutraceuticals, agrochemicals, and pigments.

Methods are broadly categorized as dry milling and wet milling. Dry milling uses equipment such as jet mills, ball mills, hammer mills, and pin mills to fracture particles. Jet mills employ high-velocity gas to collision-fracture particles, avoiding substantial thermal load. Wet milling disperses solids in a liquid and applies grinding in media mills or high-shear homogenizers, which can yield finer particles while reducing dust and heat buildup.

Key considerations include achieving a narrow particle-size distribution and avoiding chemical or polymorphic changes, thermal degradation, or contamination from milling media. Process parameters such as feed rate, grinding media, gas pressure, and milling time influence outcomes. Scale-up from laboratory to production can be challenging due to heat generation and equipment limits.

Outcomes are assessed by particle-size distribution measurements, often by laser diffraction or electron microscopy, and by dissolution testing for pharmaceutical applications. Micronization supports enhanced solubility of poorly soluble compounds and is frequently used with strategies such as solid dispersions or nanocrystal formulations.