drug solubility and dissolution rate 3 Flashcards
What are cyclodextrins?
enzymatically modified starch
they have outer hydrophilic surface and hydrophobic inner surface
what are cyclodextrins are used for?
mainly used as complexing agents to increase the aqueous solubility of substances poorly soluble in water.
what are surface active agents (surfactants)?
they reduce the surface tension at an interface without requiring large concentration.
they have hydrophilic or polar head group and lipophilic chain
what is HLB (hydrophile lipohile balance)
The balance of the polar head group and non polar chain.
Characteristics of polar region?
has affinity for water
capable of pulling long hydrocarbon chain into water
what are the classification of surfactants? (charged carried by the polar part)
anionic
cat-ionic
nonionic
zwitter ionic
what are properties of surfactants (micellisation)
surfactants aggregates over a narrow concentration range. these aggregates which contain 50 or more monomers are called micelles.
what is critical micelle concentration? (cmc)
the concentration of monomer at which micelle form?
what is aggregation number?
the number of monomers that aggregates to form a micelle
what factors affect the CMC
cmc may increase with increase in polarity of head group
CMC may decrease with temp and pH, a second surfactant, addition of electrolyte
What is Kraft point?
a sudden increase of the solubility of sodium soap in water with temperature
What is micellisation?
permits strong water-water interactions
an alternative mechanism to adsorption
what are the sudden (abrupt) changes in physical properties of surfactants at CMC?
osmotic pressure
turbidity
electrical conductance and surface tension
