Solid dispersions of the antidiabetic drug glibenclamide and polyethylene glycol 4000 (macrogol 4000) were prepared by the
melting method in order to increase the solubility of this poorly water-soluble compound. The temperature/composition phase
diagram of the components was analyzed by hot-stage microscopy and differential scanning calorimetry, showing a monotectic.
Polarized light hot stage microscopy and X-ray-powder diffraction confirmed, that glibenclamide is mainly present in a non-crystalline
state after melting and solidifying of a 10% (w/w) mixture, which results in an enhanced solubility compared to physical mixtures. The solubility and dissolution rate of the
drug increases clearly with decreasing drug/polymer ratio. Moreover, it was observed for the first time that a drug could
crystallize as whiskers at the surface of aged solid dispersion particles. Besides relaxation phenomena, this crystallization
mechanism may be responsible for a deterioration of liberation properties and bioavailability of solid dispersion based drug
products with increasing storage time.