Foam containing active ingredients

Foams containing active ingredients is the name of a monograph in the European Pharmacopoeia . The monograph defines the quality requirements for medicinal preparations in which a large volume of gas is dispersed in a liquid phase (as foam ).

properties

Foams containing active ingredients contain a surface-active component which ensures that the foam is formed. They are intended to be applied to the skin or mucous membrane (e.g. cutaneous , rectal or vaginal ). They are usually formed from a liquid preparation in a pressure vessel during application.

Foam aerosols consist of an oil-in-water emulsion . The dispersion consists of a liquid, highly volatile propellant that is dissolved in a lipid component ( vegetable oil or liquid paraffin ). Anionic or nonionic surfactants serve as emulsifiers . When it escapes from a special foam valve, the emulsion is inflated by the expansion of the dissolved propellant gases. With the help of the propellant gas concentration, which is generally much lower in foam aerosols than in other aerosol preparations, and by choosing the emulsifier, the desired foam properties can be achieved.

The advantages of this form of application are the long residence time at the site of action and the fact that large surfaces can be treated.

Containers

The container is provided with an applicator consisting of a valve and a spray head . Preparations intended for use on large open wounds or severely injured skin must be sterile. The pressurized gas containers contain compressed gases (usually nitrogen, carbon dioxide or nitrous oxide ). If non-liquefiable gases (e.g. nitrogen) are used, the pressure will decrease during emptying. Complete emptying is not possible.

Check for purity

The test for purity according to the European Pharmacopoeia includes tests for the relative density of the foam, the expansion time and, if necessary, for sterility.

literature

• European Pharmacopoeia, 8