ABSTRACT
The majority of protein drugs are delivered by the injection route, although there is an increasing interest in alternative delivery routes, e.g., pulmonary. Ready-touse liquid formulations are preferred injectable dosage forms because they are considered easier to manufacture and administer. However, the majority of proteins are not suffi ciently stable in aqueous media to provide adequate commercial shelf-life and this limits the development of protein pharmaceuticals as readyto-use injectables. Freeze-drying is an established process to increase long-term stability of proteins and achieve an acceptable shelf-life (1). In some cases, as with proteins intended for administration by inhalation, spray-drying is used (2). It is also possible to simply dry protein solutions slowly at ambient temperatures under vacuum (3). This chapter deals with freeze-dried protein formulations as they are the most common commercial dosage forms. However, general principles can be applied to other dehydration processes such as spray-drying and vacuum-drying.
