Assessment of the wettability of pharmaceutical powders

There is considerable interest in the assessment of the wettability of pharmaceutical powders, as the data can be used to give indications of product performance (in terms of a crude predictor of rates of drug release from dosage forms, or as a guide to the interfacial interactions between components of a formulation). However, contact angle methods for powders are problematic, in particular because powders have heterogeneous and rough surfaces, and these are often capable of rapid changes in properties. The different approaches to contact angle assessment are reviewed, and some advantages of vapour sorption experiments are discused.