D. Colloidal Stability Flashcards
What is an emulsion ?
A liquid-in-liquid colloid
What is a suspension ?
A solid-in-liquid colloid
Why may we have to use dispersed systems ?
- Drug is hydrophobic so cannot be dissolved in water so dissolved in oil and oil is dispersed in isotonic water carrier to dorm an emulsion
- Easier to administer to children
What are the possible emotions ?
W/O/W
O/W/O
True or false?
Dispersion of a liquid in a second immiscible liquid. This created a molecular funk if emulsifier at the interface .
True
What is the purpose of an emulsifier ?
It’s for stability and it is a molecular film that is at the interface of the immiscible liquid particle.
It works by slowing the process of re-separation to the original low energy system.
How are emulsions produced?
They require a large input of energy which is produced by HOMOGENIZATION
What is the most common form of emulsion?
Oil in water
Can re-separation to the original low energy system be prevented ?
No, it can only be slowed down by the emulsifier
How does an emulsifier work ?
The emulsifier positions itself at the interface between the two phases O/W emulsion
The hydrophobic part will position itself in the oil droplet
The hydrophilic part will position itself in the water.
Overall this created a charged layer around the droplet (at the interface)
Repulsion of similar charged prevent droplets from approaching each their and this is what stabilised the emotion and helps slo down re-separation
What a re the applications of emulsions ?
- Intravenous (TPN) for patients who are in intensive care. This can simulate chylomicrons and fats can be absorbed from the GIT
- delivery of hydrophobic drugs
- Oral (enteric feed and oral delivery of hydrophobic drugs)
- Intramuscular (W/O emulsions for sustained release and emulsion vaccine adjuvants)
How would you make a hydrophobic drug into an emulsion ?
Hydrophobic drug will only be soluble in oil.
This is then emulsified
Drug must be very hydrophobic (log p>5)
What could happen if the drug is not very hydrophobic (log p<5) ?
Drug will transfer through the aqueous phase and crystallise out
What can you do to a drug that is insoluble in both oil and water ?
Can solubilise drug in emulsifier solution and then use this to emulsify the oil phase
What is floccuation ?
Particles/droplets cluster together in a open structure.
These particles still maintain their individual identity and can be Reid’s-erased into their single particles/droplets by shaking
