Estimation of Drug Particle Size in Intact Tablets by 2-Dimensional X-Ray Diffractometry

The average grain size of a crystalline material can be determined from the γ-profile of Debye rings in 2-dimensional X-ray diffraction frames. Our objectives were to: (1) validate the method for organic powders and use it to determine the grain size in intact tablets, and (2) demonstrate the pharmaceutical application of this technique by determining the grain size of the active pharmaceutical ingredient in marketed formulations. Six sieve fractions of sucrose were prepared and the particle size distribution was confirmed by laser diffraction. Their average grain size was determined from the 2-dimensional X-ray diffraction frames by the γ-profile method. For particles <90 μm (based on sieving), the average particle size determined by the 3 methods were in good agreement. When these particles were compressed, there was no discernible change in the sucrose grain size in tablets. When the particles were >250 μm, compression resulted in a mixture of large grains and fine powder. The grain size of acetaminophen in 11 marketed tablet formulations was determined to be either ∼35 μm or ∼80 μm. This nondestructive technique can therefore be potentially useful to estimate the grain size of crystalline formulation components in intact tablets.