Powder mixing.

The factors affecting powder mixing are reviewed. Methods of analyzing a random mix are discussed (indices, the Poisson distribution, and analyses of variance [ANOVA]). The influence of particle size, shape, and density are described, along with scale of scrutiny and sampling. Segregation and agglomeration are major problems in powder mixing, and their prevention and minimization are therefore paramount. Ordered mixing reduces segregation, but also introduces other problems. Regulating the particle size of the drug and altering particle shape minimizes segregation and agglomeration.