Preformulation Flashcards
What do surfactants do?
Reduce surface tension
How is surface tension measured?
Force / contact perimeter
At what concentration will micelles form?
Critical Micelle Concentration (CMC)
What is Traube’s Rule?
Concentration to achieve a certain surface tension decreases by 3 fold with the addition of CH2 to the surfactant molecule
What is an emulsion?
Two immiscible liquids form a macrostable (not entirely stable) mixture
What are the types of emulsions?
Single Emulsion
- W/O
- O/W
Double emulsion
- W/O/W
- O/W/O
primary emulsion liquids in another liquid
How does an emulsifier work?
Forms interfacial film around the droplets, reducing the interfacial energy making it more stable and more likely to exist as a droplet
What is Bancroft’s Rule?
“The phase in which the emulsifier is more soluble is the continuous phase”
Hydrophillic emulsifier = O/W
Hydrophobic emulsifier = W/O
What is HLB scale used for?
As a measure of hydrophobicity/lipophobicity
0-10 = lipophilic
10-20 = hydrophillic
What are the 7 types of topical treatments?
- ointment
- creams
- gel
- lotion
- foam
-spray - patch
What is the difference between solution, suspension and emulsion?
Solution - all drug is dissolved (homogenous)
Suspension - solid particles dispersed in liquid
Emulsion - liquid dispersed in liquid
What are some pros and cons of the topical route?
+ non-systemic effect
+ better drug targeting
+ convinient
+ avoids GI drug degradation
- low skin-permeability, only select drugs
- difficult to dose accurately
- skin irritation
What are the different types of mixtures?
Postive - mixes spontaneously
Negative - separates spontaneously
Neutral - neither
Strategies for mixing a solid and a liquid.
Solid:
Connective Mixing - Bulk Transport
Shear Mixing - moving layers at different velocities
Diffusive - introducing air
Liquid:
Bulk transport
Turbulent mixing - group of molecules at different velocities
Diffusion
What type of mixture is good for potent drugs?
Ordered Mixture
-microionised particles absorb on surface of larger carrier particles
- higher uniformity
