Water vapour sorption by pharmaceutical sugars

Sugars ave probably the most widely used pharmaceutical excipients in solid and liquid dosage forms, and they can interact strongly with water vapour in their environment due to their hydrophilic nature. Crystalline sugars typically exist in anhydrous and hydrated forms, and these forms primarily interact with water vapour by adsorption and deliquescence mechanisms. Amorphous sugars usually absorb water into their bulk structure, and may experience marked changes in their physicochemical properties as a consequence. This review describes the mechanisms and phenomenology of water vapour sorption by pharmaceutical sugars, and provides an overview of the interaction phenomena that need to be considered when developing sugar-containing pharmaceutical dosage forms.