Emulsion C Flashcards
(30 cards)
What is a pharmaceutical emulsion?
A mixture of two immiscible liquids (oil and water), one dispersed in the other using an emulsifier.
What are the two main types of emulsions?
Oil-in-water (o/w) and water-in-oil (w/o).
What is a multiple emulsion?
An emulsion within an emulsion, such as w/o/w or o/w/o.
Why are emulsions thermodynamically unstable?
They tend to revert to separate phases unless stabilized by emulsifiers.
List one advantage of emulsions as dosage forms.
They can enhance bioavailability or reduce side effects.
What is the Bancroft Rule?
The phase in which the emulsifier is more soluble becomes the continuous phase.
What are the three primary types of emulsifiers?
Surface active agents, natural polymers, and finely divided solids.
Give an example of each type of emulsifier.
Sodium lauryl sulfate (surface active), acacia (natural polymer), bentonite (solid).
What are humectants and give an example.
Substances that prevent water loss; e.g., glycerol.
Why are antioxidants used in emulsions?
To prevent oxidation and rancidity of oils.
What are two physical instabilities in emulsions?
Flocculation and coalescence.
What is Ostwald ripening?
Smaller droplets dissolve and redeposit onto larger ones, increasing droplet size over time.
What causes phase inversion?
Change in temperature or interaction with additives.
What determines emulsion type using dilution tests?
Emulsions mix only with liquids matching their continuous phase.
How are emulsions used in dermatology?
As creams or lotions that deliver drugs through the skin.
What type of emulsions are commonly used orally?
Oil-in-water (o/w) emulsions.
What are parenteral emulsions used for?
IV delivery of nutrients or poorly soluble drugs.
Why is preservative choice important in emulsions?
Preservatives can partition between phases and be inactivated.
Give an example of a preservative used in emulsions.
Benzoic acid or parabens.
What is the hydrophile-lipophile balance (HLB)?
A scale (0–20) that indicates surfactant solubility in water or oil.
What HLB value favors o/w emulsions?
Higher HLB (more hydrophilic).
What is the Phase Inversion Temperature (PIT)?
The temperature at which an o/w emulsion switches to w/o.
What influences rheology in emulsions?
Continuous phase composition, phase volume ratio, and droplet size.
What flow property is desirable in topical emulsions?
Pseudoplastic or plastic flow.
