|
|
|
Physico-chemical and analytical characterisation of drugs
Physicochemical and analytical characterisation of drugs is similar to the preformulation studies department in a major drug company. This area is key to rapid progression of the ideas and concepts in areas such as oral, lymphatic, transdermal and respiratory drug delivery.
Physicochemical characterisation deals with the skills and techniques needed to provide research and development staff with the basic chemical information that is germane to successful design and development of a suitable formulation to deliver a drug to its site of action. This information includes measured solubility in different solvents, acid-base equilibria, oil-water partition coefficients, critical micelle concentration ranges and concentration-time profiles from which degradation rate constants may be extracted. Drugs which are to be formulated as solids require extensive information on the solid state, such as melting point, enthalpy and entropy of fusion, crystal morphology, surface properties and particle analysis. Acquisition of such data is also critically important in characterising the excipients that may be needed in formulations. In addition to characterisation data on the individual drugs or excipients, methods for characterising the interactions between drugs, or between drugs and excipients, is also important in formulation design, and in accounting for the biopharmaceutical properties of drugs. Another aspect of the characterisation of drugs and excipients includes their spectroscopic characteristics, especially UV-VIS, fluorescence, infra-red, nuclear magnetic resonance and mass.
Macromolecular drugs and excipients present special difficulties in characterization, mainly due to their potential for highly organized and relatively weakly stabilised structures. The same may be said for complex delivery systems, such as micelles, microemulsions, liposomes and vesicles. While full elucidation of such complex organised structures requires specialities outside Pharmaceutics (e.g., molecular modelling, nuclear magnetic resonance and X-ray diffraction methods), available skills and facilities for characterisation of these more complex compounds and systems include scanning microcalorimetry, hot-stage microscopy and temperature-controlled circular dichroism spectrometry.
Specific research projects include:
|
