L50: Liquid dosage forms Flashcards
(43 cards)
What are emulsions in pharmaceutical terms?
Disperse systems where an insoluble liquid is dispersed in a second liquid phase.
What is the disperse phase in an emulsion?
The phase that is sub-divided.
What is the continuous phase in an emulsion?
The phase in which the disperse phase is distributed.
List four uses of pharmaceutical emulsions.
Cream formulations (topical), parenteral nutrition, oral administration, rectal administration of antiepileptic agents.
Name three additives in the emulsion and their purpose.
Vanillin (flavouring), Chloroform (flavour/preservative), Benzoic Acid Solution (preservative).
Why are emulsions used for drugs with low aqueous solubility?
The drug is dissolved in the internal oil phase and oil droplets are absorbed on oral administration.
what are advantages of emulsions?
- delivery of drugs with low aq solubility
- drug dissolved in internal oil phase
- taste masking
- administration of oils with therapeutic effect
How can emulsions reduce irritation in topical applications?
The drug is placed in the internal phase (o/w).
What is a patient benefit of emulsions for people with dysphagia?
Easier swallowing compared to solid dosage forms.
What is one nutritional use of emulsions?
Total parenteral nutrition.
what are disadvantages of pharmaceutical emulsions?
- thermodynamically unstable, formulations need to ensure they emulsions are 1 face
- difficult to manufacture
what are the types of emulsions?
- O/W: oil is dispersed, water is external phase
- W/O: water is dispersed, oil is external phase
- Multiple emulsions(O/W/O):: disperse phase contains droplets of another phase
what are criteria for acceptable emulsions and creams?
- stable, no phase separation
- good flow properties
- easy to spread
- aesthetically pleasing/ texture
- suitable flavour
what determines the emulsion type?
- its defined by stability of droplet phase
- the phase with the lower stability forms the external phase
- the phase with the higher stability forms the internal face
What determines the type of emulsion formed?
Phase volume of internal phase, chemical properties of film surrounding internal phase, and viscosities of phases.
What phase volume ratio is typically stable in practice?
Around 50%.
What is cracking in emulsions?
Irreversible coming together of the internal phase, leading to complete separation between the 2 layers due to the destruction of the film at the interface
What can cause cracking?
wrong emulsifiers, incompatible excipients, temperature, microbial spoilage.
What maintains a defined distance between droplets in a flocculated emulsion?
Secondary interactions like van der Waals forces.
Can flocculated emulsions be re-dispersed?
Yes, by shaking.
What causes creaming in emulsions?
Density differences between oil and water phases.
- can be prevented if the density difference between the 2 phases is 0
How can creaming rate be reduced?
Reduce particle size or increase viscosity.
What is phase inversion in emulsions?
A switch between o/w and w/o types.
What triggers phase inversion?
Exceeding the critical phase volume ratio.
- o/w 74:26
- w/o 40:60
