Definition
An emulsifying agent (or emulsifier) is a substance that stabilizes an emulsion by improving its kinetic stability.
Emulsifiers work by reducing surface tension at the interface between the oil and water phases, making it easier to mix and stabilize the two phases.
In pharmaceuticals, emulsifiers can also affect the bioavailability and release profile of the drug.
Types of Emulsifying Agents
1) Surfactants:
The most common emulsifiers, which include anionic, cationic, nonionic, and amphoteric surfactants.
They possess both hydrophilic (water-attracting) and lipophilic (oil-attracting) properties, enabling them to reduce surface tension between the two phases.
2) Hydrocolloids:
High molecular weight compounds, often polymers, that stabilize emulsions by increasing viscosity and forming a protective layer around the droplets.
They help maintain the stability of the emulsion by preventing the droplets from coalescing.
Selection Criteria for Emulsifying Agents
Compatibility with the drug and other formulation components
Ability to form a stable emulsion
Safety and non-toxicity
Influence on drug release and bioavailability