Definition
An emulsion in pharmaceutics is a heterogeneous system consisting of two immiscible liquids (often oil and water), where one liquid is dispersed in the other as small droplets.
Emulsions are typically unstable and require stabilizing agents (emulsifiers) to maintain the dispersion.
Classification of Emulsions:
1) Oil-in-Water (O/W) Emulsions:
Here, oil droplets are dispersed in a water phase.
Commonly used in oral, intravenous, or topical pharmaceutical formulations as they are more compatible with the body's aqueous environment.
2) Water-in-Oil (W/O) Emulsions:
In these, water droplets are dispersed in an oil phase.
Often used in topical formulations like moisturizing creams or ointments to create a water-resistant barrier.
3) Multiple Emulsions:
These can be water-in-oil-in-water (W/O/W) or oil-in-water-in-oil (O/W/O) systems.
Used in specialized drug delivery applications to control the release of active ingredients.