Diffuse Reflectance Studies of Solid-Solid Interactions

Tetracycline and its derivatives, bishydroxycoumarin, and methantheline bromide have been studied by diffuse reflectance spectroscopy for possible solid-solid interactions with various metallic adjuvants. Examination of the spectra of some of these drug-adjuvants systems show rather small spectral changes, while other spectra show large bathochromic and hyperchromic changes, new band formation, and visual color changes which are indicative of charge-transfer interactions. Although these interactions vary in variety and intensity, they may significantly alter the availability and activity of the medicinal agent in pharmaceutical dosage forms.