[X-ray diffractometry in the analysis of drugs and pharmaceutical forms].

As a consequence of the importance of solid drug substance characterization, analytical tools such as X-ray diffractometry (powder and single crystal methods) are usually employed in the pharmaceutical field. The diagnostic power of X-ray powder diffraction in identifying crystalline compounds, even in multicomponent mixtures, and in showing the non-crystalline ones, has brought about the usual characterization through the X-ray powder diffraction pattern of polymorphic, pseudopolymorphic, and amorphous drugs and of some drug-carrier systems such as solid dispersions, glass dispersions, solid surface dispersions, physical mixtures, eutectics, solid solutions, addition and inclusion compounds, etc. Moreover this technique is also used in the qualitative and quantitative analysis both of drug mixtures and dosage forms, and also in the study of relationships between crystal habit and technological characteristics of pharmaceutical formulations. Single crystal methods are employed for calculating the unit cell lenghts and angles, for indexing powder diffraction patterns, and for demonstrating the crystal and molecular structure of the drug. After a picture of the solid state properties and the X-ray characteristics, as well as of the interaction between X-rays and solid matter, the main pharmaceutical applications of X-ray diffraction are described.