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Almost 100 years after the discovery of the Raman scattering phenomenon, related analytical techniques have emerged as important tools in biomedical sciences. Raman spectroscopy and microscopy are frontier, non-invasive analytical techniques amenable for diverse biomedical areas, ranging from molecular-based drug discovery, design of innovative drug delivery systems and quality control of finished products. This review presents concise accounts of various conventional and emerging Raman instrumentations including associated hyphenated tools of pharmaceutical interest. Moreover, relevant application cases of Raman spectroscopy in early and late phase pharmaceutical development, process analysis and micro-structural analysis of drug delivery systems are introduced. Finally, potential areas of future advancement and application of Raman spectroscopic techniques are discussed.

The objective of the present study was to determine the solid state solubility and miscibility of naproxen in poly(vinylpyrrolidone) (PVP) and the mutual interaction using the standard thermodynamic models and thermal analysis. Solid dispersions were prepared by spray drying several compositions of naproxen and PVP with different molecular weights, viz., PVP K 12, PVP K 25 and PVP K 90, and analyzed using modulated differential scanning calorimetry (mDSC). The kinetic miscibility limit in terms of a single mixed phase glass transition temperature was found to be relatively similar for the dispersions containing PVP with different chain lengths (>or=50% w/w drug in PVP). But the systems with different PVP followed diverse patterns of composition dependent mixed phase glass transition temperature as well as the degree of plasticization by water. The crystalline solid solubility values of naproxen in PVP estimated by using its solubility data in n-methylpyrrolidone, a low molecular weight analogue of PVP, were 6.42, 5.85 and 5.81% w/w of drug in PVP K 12, PVP K 25 and PVP K 90 respectively. The values estimated for corresponding amorphous solubility showed no marked difference. The remarkable difference between thermodynamic solubility/miscibility and kinetic miscibility implied that naproxen was highly supersaturated in the PVP solid dispersions and only stabilized kinetically. The negative value of the drug-polymer interaction parameter (-0.36) signified the systems to be favorably mixing. The melting point depression data of naproxen in PVP pointed to the composition dependence and chain length effect on the interaction. The moisture sorption by the physical mixtures not only provided the composition dependent interaction parameter but also conferred an estimate of composition dependent miscibility of naproxen in PVP in the presence of water.

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The solid dispersions are significantly supersaturated with respect to both crystalline solubility and amorphous miscibility demonstrating the influence of manufacturing methodology.