Excipients that facilitate amorphous drug stabilization

The importance of the amorphous state in studying bioavailability of poorly water-soluble drugs cannot be over-emphasized. The higher free energy and therefore the apparent high solubility of the amorphous phase are some of the advantages for promoting the amorphous phase, as compared to its crystalline counterpart. It is well known that the amorphous phase is thermodynamically unstable. This might result in the conversion of the metastable form to its stable crystalline form during storage. This conversion might also lead to product failure during storage owing to the poor dissolution properties of the crystalline form. Excipients can play a key role in preventing such a transformation during storage as well as maximizing the therapeutic efficacy of the amorphous material. This book chapter intends to highlight the delivery issues pertaining to amorphous drugs with a special emphasis on the most commonly used excipients in stabilizing amorphous drug substances in formulations.