SOLID-STATE INVESTIGATIONS OF ERYTHROMYCIN-A DIHYDRATE - STRUCTURE, NMR-SPECTROSCOPY, AND HYGROSCOPICITY

The crystal structures of the commercially available form of erythromy cin A dihydrate and clarithromycin anhydrate, in addition to the struc ture of erythromycin B dihydrate, are reported in this paper. In light of the crystallographic data, analysis of the structural information provides insight into the physical properties of these pharmaceuticals . The propensity of these pharmaceuticals to form solvated structures is discussed and the hygroscopicity of erythromycin A dihydrate is inv estigated. Solid-state C-13 NMR was used to monitor changes that occur when the dihydrate form of erythromycin A is stored under conditions of low relative humidity. Although erythromycin A dihydrate retains it s crystallographic order at low humidity, as indicated by its X-ray po wder diffraction pattern, the local chemical environment is dramatical ly influenced by the loss of the water molecules and results in dramat ic changes in its solid-state C-13 NMR spectrum.