What defines collodions in a pharmaceutical context?

Collodions are defined in the pharmaceutical context as liquids that dry to form flexible films on the skin. This property is significant because collodions are primarily used in topical applications, such as for protecting wounds or delivering medications through a film-forming process. Upon application, the solvent evaporates, leaving a thin, flexible layer that adheres to the skin, thereby providing a barrier against external elements while also offering a medium for drug delivery.

This characteristic of forming a film is crucial as it differentiates collodions from other types of topical preparations. For instance, while flexible films that dissolve in water may suggest a completely different action, collodions do not dissolve in water; they remain intact even in moist conditions. Likewise, although medications with slow absorption rates might share similarities with some collodion formulations due to the presence of certain polymers or agents, it is not the defining feature of collodions. Finally, while solutions that are sticky and thick may describe certain formulations, collodions are specifically noted for their ability to dry into a film, which is essential to their function in both cosmetic and medicinal applications.