X-ray Diffraction (XRD) is applied at all phases of the drug discovery and development process in pharmaceutical formulation. XRD use begins with identification of a potential substance for therapeutic use and continues right till the final formulation culminates in the finished product. X-Ray Diffraction techniques are now widely used in drug formulation as it accelerates and improves the drug development process.
Why X-Ray diffraction (XRD) techniques are useful is because they can list the physiochemical characterisation of any solid material, whether known or unknown. Accurate characterisation is possible because of non-destructive nature of XRD and its ability to produce a unique pattern for each crystalline phase. Accurate characterisation ensures reproducibility which makes it possible to monitor its integrity when a pharmaceutical is undergoing processing, formulation, manufacturing or storage. In fact XRD analysis can be used to control the crystal structures of any novel material and derive information about the crystalline phase, the degree of crystallinity and any possible polymorphic contamination. This information is helpful in designing an accurate pharmaceutical formulation.
It has been observed that active pharmaceutical ingredients (APIs) are mostly present in crystalline form. When the crystal structure of the API is characterised using X-ray diffraction you get the exact physical and chemical properties. Once the exact properties are known, it becomes easy to formulate the pharmaceutical as well as analyse and determine the dissolution and stability. Sometimes the behaviour of the API that has been solubilized could vary with the nature of its liquid base. In such instances, the laboratory testing team carries out analysis to determine the conditions at which the API will change and that helps to determine the solubility or dissolution rate. Knowing the solid-state properties right in the early stages of drug development prevents problems during manufacture of the formulation.
Since the polymorphic crystalline forms all have different patterns, it is possible to quantify them in mixtures with XRD methods. This is very important for controlling the polymorphic purity of an API especially if they have different physical properties. When crystalline API cannot be prepared using a single crystal then powder X-ray diffraction techniques are applied to derive at the structures of the crystalline molecules. With the advancement in technology as well as computing it has now become a common practice in testing laboratories to determine structures with XRD.
XRD can prove useful in fine-tuning the performance of the formulation and can lead to more drug innovation.In drug development, one of the areas where XRD plays a key role, besides identification of substances, is stability of the drug during long term storage. A formulation can easily be screened for changes and analysed with XRD techniques. XRD instrumentations can also measure bulk samples. In fact even whole pharmaceutical tablets can be measured, with making just a few adjustments for the curved surface of the tablet so that the curvature is reduced and the measurement is accurate.In this way pharmaceuticals carry out XRD analysis so that they can avoid any adverse effects in drug delivery.