introduction to medicinal products part 4 Flashcards
what is an emulsion?
dispersion of liquids that are immiscible
two types of emulsions?
water in oil w/o
oil in water o/w
which emulsion is more preferred by patients and why?
oil in water because less greasy and can mask the unpleasant taste and smell
why are o/w emulsions faster to absorb?
because drug is already dissolved
what is important in making drugs in the form of an emulsion?
stability, if unstable then unexpected drug release which is dangerous
what is cracking?
emulsion separating and no longer uniformaly distributed
what are the causes of cracking?
temperature change, bacteria growth
what form are ointments and pastes in?
semi-solid
what are ointments and pastes for?
prevent trans epidermal water loss, helping with skin hydration
difference between pastes and ointments?
pastes have a high concentration of drugs dispersed in it
what determines the stability of emulsion?
emulsifier and oil used
how does an emulsifier increase stability in an emuslion?
decreases the o/w interfacial tension
examples of emulsifiers for pharmaceutical separation?
surfactants, proteins, polysaccharides, magnesium hydroxide
what emulsifier effects the type of emulsion produced?
if its polar or non-polar
how are emulsifier characteristics told apart?
HLB numbering system
what is the structure of an amphiphile?
hydrophobic tail and hydrophilic head
what is creaming?
flocculates and coalesce forms and rise to the surface
why are SDS and CTAB hydrophilic?
their ionic charge
examples of simple emuslifiers?
SDS, CTAB, Cetostearyl alcohol
what are mixed emulsifiers?
charged and non-ionic, dense interfacial film
why are single charged amphiphiles not used as emulsifiers?
repel
sparse interfacial film
where are hydrophobic emulsifiers located on HLB?
near the bottom
where are hydrophilic emulsifiers located on HLB?
near the top
what is polyoxythylene?
a water soluble group
what is polyoxythylene used for?
liquid vehicle, solid polymer, substituent (added to make molecules more hydrophilic
what happens as the chain length of the polyoxythylene increases?
more vicious
liquid to solid
more hydrophilic
what do all alkyl chains have in common?
searate C18
what makes proteins aphiphiles?
hydrophobic region and hydrophilic regions
how do proteins prevent coalescence?
‘absorb at interfaces’, forms surface network, barrier layer
how are proteins used as stabilizing agents?
‘bridge between droplets’
why are proteins widely used in food products
good emulsifiers
what are two natural emulsifiers in food?
milk, lecithin
what kind of emulsion is milk?
‘o/w stabilised by protein’
what is the basis of many emulsifiers?
sorbitan
why are sorbitan emulsifiers used?
cheap, four different OH groups so substituents can hang onto them, hydrocarbon substituents can be used to increases hydrophobicity, polyoxyethylene substituent can be added to increases hydrophilicity
what is a HLB?
Hydrophile Lipophile Balance scale
what is the diagram of polyoxythylene glycol?
slide 16
