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The pharmaceutical term “emulsion” is most time used to
indicate preparations prepared for internal use. Emulsions
for external use are always given a different title
that it focus may indicate their use, e.g. lotion and cream
(Christopher and Dawn, 2008).
An emulsion may be defined as a biphasic system
consisting of two immiscible liquids, one of which (the
dispersed phase) is finely and uniformly dispersed as
globules throughout the second phase (the continuous
phase). Since emulsions are a thermodynamically
unstable system, a third agent, the emulsifier is added to
stabilize the system (Agarwal and Rajesh, 2007).
Emulsifier stabilizes the system by forming a thin film
around the globules of dispersed phase (Javed et al.,
2008). Either the dispersed phase or the continuous
phase may vary in consistency from that of a mobile
liquid to semisolid (Alfred, 2005). Thus, pharmaceutical
emulsions range from lotions (low viscosity) to creams
(high viscosity). The particle size of the dispersed phase
commonly ranges from 0.1 to 100 µm (Agarwal and
Rajesh, 2007).
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