Laser Raman investigation of drug-polymer conjugates: sulfathiazole-povidone coprecipitates.

Laser Raman spectroscopy is used for the investigation of the drug-polymer conjugates, sulfathiazole-povidone. Specifically, Raman spectra, both in the lattice vibration and the intramolecular vibration regions, are used to characterize various polymoprhic forms of sulfathiazole. It is found that sulfathiazole exists in two unsolvated forms, untreated sulfathiazole and another form grown from propanol. The crystals grown from ethanol include varying amounts of ethanol depending on the growth condition. The nature of the povidone-sulfathiazole coprecipitates of various compositions are studied. We find no evidence of any new polymorphic form of sulfathiazole in these coprecipitates. The coprecipitates are found to consist of one of the unsolvated forms of sulfathiazole.

Laser Raman investigation of pharmaceutical solids: griseofulvin and its solvates.

Laser Raman spectroscopy is convenient for characterizing griseofulvin solvates and investigating solute-solvent interactions and desolvation. The spectra of both lattice and intramolecular vibrations were monitored. A new solvate of griseofulvin wih bromoform was characterized by Raman spectroscopy. A temperature-dependence study of the solvates of griseofulvin with chloroform, and benzene revealed no phase transformation or chemical change. In the benzene solvate, only weak Van der Waals interactions existed between the solute and solvent. However, in solvates with chloroform and bromoform, a weak hydrogen binding existed between the proton of the solvent and the C = O group of the benzofuran ring in griseofulvin. Examination of desolvation in these solvates revealed that the crystal did not go through any intermediate structure during desolvation. As the solvent molecule escaped, the lattice reverted to the structure of unsolvated griseofulvin.