Dear ,
Greetings of the day.
Can you specify , why not Sifting operation is carried out after micronization.
Most the API industries following the same. Why.
Thanks
Regards
Dr. A.K. Shrivastava

methods of micronization ppt

Abstract

Micronization is the process of reducing the average diameter of a solid material's particles. Usually, the term micronization is used when the particles that are produced are only a few micrometers in diameter. However, modern applications (usually in the pharmaceutical industry) require average particle diameters of the nanometer scale.The use of drug powders containing micronized drug particles has been increasing in several pharmaceutical dosage forms to overcome the dissolution and bioavailability problems. Most of the newly developed drugs are poorly water soluble which limits dissolution rate and bioavailability. The dissolution rate can be enhanced by micronization of the drug particles. The properties of the micronized drug substance such as particle size, size distribution, shape, surface properties, and agglomeration behaviour and powder flow are affected by the type of micronization technique used. Mechanical communition, spray drying and supercritical fluid (SCF) technology are the most commonly employed techniques for production of micronized drug particles but the characteristics of the resulting drug product cannot be controlled using these techniques. Hence, a newer technique called in situ micronization is developed in order to overcome the limitations associated with the other techniques. This review summarizes the existing knowledge on in situ micronization techniques. The properties of the resulting drug substance obtained by in situ micronization were also compared.

Introduction
In the recent years, it is estimated that 90% of the New Chemical Entities (NCEs) are poorly water soluble compounds which come under Biopharmaceutical classification system (BCS) class II or class IV (Filippos and Yunhui, 2008). According to BCS, dissolution is the rate limiting factor for the drug absorption rate of both class II and class IV compounds which result in poor bioavailability. Owing to their low poor water solubility and bioavailability, several potential drugs are abandoned in pharmacological screenings (Robinson, 1993 and Rasenack and Muller, 2002a). It is a well-known major hurdle for the formulators to handle such poorly water soluble compounds. The chemical and physical properties of the poorly soluble compounds can be optimized to improve oral bioavailability of water insoluble compounds. Various formulation strategies have been reported to improve solubility and dissolution rate of poorly water soluble drugs such as inclusion of complexation with cyclodextrins, solid dispersion, salt formation, particle size reduction, use of surfactants, cosolvency, hydrotrophy, etc. Amongst above mentioned methods, the most reliable technique to improve the dissolution rate is micronization (Rasenack and Muller, 2004 and Jalay, 2011).

Micronization is a term used to describe size reduction technique where the resulting particle size distribution is less than 10 μ. Since the morphology of particles, particle size and size distribution produced in different industries are usually not appropriate for the subsequent use of such materials; particle design has been gaining importance in manufacturing advanced coating materials, microsensors, polymers, pharmaceuticals, and many other chemicals. The present article thoroughly reviews about in situ micronization as a novel micronization technique.