Ionic emulsifiers

S.u. oil-in-water emulsifiers.

Cationic (or ionic) emulsifiers are emulsifiers that have a positively charged functional group but not additionally a negatively charged group. Like any emulsifier, cationic emulsifiers are composed of a polar and a non-polar part. Different alkyl groups serve as the non-polar part. The polar group is usually a quaternary ammonium unit, so they are often tetraalkylammonium salts. Cationic emulsifiers are also called inverter soaps. In pharmaceutical preparations, however, they are used less as emulsifiers than because of their antimicrobial effect.

Possible emulsifiers are e.g. betaines, proteins, lecithin, gelatine and casein.

Ionic emulsifiers such as sodium stearyl sulfate in the hydrophilic base of AB are characterized by excellent emulsifying properties, but are problematic due to their incompatibility with cationic agents (loss of efficacy) and additives (breaking of the emulsion). Therefore, the water-containing non-ionic hydrophilic ointment of the DAC is to be preferred for prescription.

Amphoteric, surface-active molecules (containing both anionic and cationic groups in the molecule), which can act as both oil-in-water and water-in-oil emulsifiers