Lab 6 Part 1 Flashcards by amanda kastel

define an emulsion

a mixture of two immiscible liquids where one phase is finely dispersed in the other and stabilized using an emulsifier

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as mentioned, an emulsion is a mixture of 2 immiscible liquids where one phase is finely dispersed in the other and stabilized using an emulsifier.

the 2 immiscible liquids are generally what?

oil and water

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the liquid dispersed in the other liquid is called the ___ or ___ phase

dispersed or internal phase

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the liquid in which the other is dispersed is called the __ or __ phase

continuous or external phase

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emulsions are classified in ___ types:

2 types based on whether the water or oil is dispersed as the fine droplets

o/w – oil is dispersed phase, water is external

w/o – water is dispersed phase and oil is external

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are there any other types of emulsions besides w/o or o/w?

yes:

multiple emulsions (emulsion dispersed within an emulsion) w/o/w or o/w/o

microemulsion (droplet size less than 200nm)

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multiple emulsions and micro emulsions are generally prepared using what?

commercial technology

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what 2 tests are used to determine the type of emulsion

dilution and dye tests

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explain how the dilution method to determine the type of emulsion works

when water is added to a w/o emulsion, the water is not incorporated in the emulsion and remains as a second layer

in the case of an o/w emulsion, a separate oil layer would be observed

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explain how the dye method of determining the type of emulsion works

when a dye that is soluble to the external phase is added, the dispersed phase will look like colorless droplets when viewed under a microscope

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name 3 ways in which emulsions can be administered

orally
IV
topical

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name some emulsions that can be administered orally

mineral oil
oil soluble vitamins
products for enteral feeding

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what emulsions can be given IV

IV lipids

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what emulsions can be given topically

ointments
creams
lotions

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oral emulsions are ___ ___

pourable liquids

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oral emulsions are generally w/o or o/w? why?

generally o/w because the oily phase doesn’t taste as good and is also more difficult to flavor

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true or false

emulsions for external applications are either water in oil OR oil in water and may be liquid or semisolid

true

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topical ___/___ preparations are more occlusive and emollient while __/___ are easier to remove/wash

w/o are more occlusive and emollient

o/w are easier to remove/wash

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emulsifers ____ the surface tension

why

emulsifiers LOWER the surface tension which helps to break up the large droplets into smaller ones and preventing their coalescence

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what is the 1st theory of emulsification

the surface tension theory – emulsifiers lower the surface tension which helps to break up large droplets into smaller ones and prevent their coalescence

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what is the oriented wedge theory

based on hydrophilic and hydrophobic properties

emulsifiers tend to orient their hydrophilic and hydrophobic portions between the external and internal phase (based on solubility)

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according to the oriented wedge theory, an emulsifier that is more hydrophilic will form __ in ___ emulsion

why?

oil in water

this is because the hydrophilic portion is not large enough to form a wedge in the droplet

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explain the interfacial film theory

the emulsifying agent is adsorbed on the surface of the dispersed droplets and thus prevents contact with the external phase

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lowering of surface tension is important in the formation of the ________ and orientation and interfacial film theories are required to…..

lowering surface tension is important in forming the initial dispersion

oriented wedge and interfacial film are required to prevent COALESCENCE and thus maintain stability

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in the HLB system, a diagram of an emulsifier will have the ____ portion as the head and the ___ portion as the tail

hydrophilic head and hydrophobic tail

____ devised a method to categorize the emulsifiers based on the ratio of hydrophilic and lipophilic portions in the emulsifier

griffin

what is the term for the "ratio" that griffin devised to categorize emulsifiers based on the ratio of hydrophilic and lipophilic portions in the emulsifier

HLB value

each emulsifier is assigned an HLB value to indicate its degree of _____

POLARITY (hydrophilicity)

which emulsifier is assigned a value of 1? which emulsifier is assigned 40? what do these values mean

1 = Oleic acid (LEAST POLAR) 40 = SLS (sodium lauryl sulfate) MOST POLAR

substances with an HLB ranging from 1-10 are used for....

antifoaming water in oil wetting properties

substances with an HLB value ranging from 10-20 are used to form....

oil in water emulsions

emulsifiers that have an HLB similar to that of the __ phase are used in preparing emulsions

oily phase

true or false two or more emulsifiers CANNOT be used to achieve the desired HLB

false -- you can use 2 or more to achieve the desired HLB

HLB values 3.5-6

W/O emulsifier

HLB values 7-9

wetting agent

HLB values 8-18

O/W emulsifier

HLB values 13-15

detergent

HLB values 15-18

solubilization

an emulsifier has 2 distinct actions:

1. promote the formation of an emulsion - make easier to prepare by reducing droplet size and aid in stability 2. controlling the type of emulsion -- O/W or W/O

the type of emulsion is related to the ____ of the emulsifier

HLB value

the EFFICIENCY of an emulsifier is related to its....

chemical structure (ester, partial ester, saturated lipophilic group, surfactatant)

emulsifiers with an HLB value of ____ have EQUAL ATTRACTION TO OIL AND WATER

Emulsifiers with an HLB value greater than 10 are more ___ and useful for which emulsion?

more hydrophilic and useful for o/w emulsions

emulsifers with HLB values LESS than 10 are more ____ and used for which emulsions

hydrophobic and used for water in oil emulsions

the HLB of the emulsifier used in the preparation depends on what 2 things

the HLB of the oil the type of emulsion(w/o or o/w)

lanolin anhydrous requires what HLB

for an o/w emulsion between 10-15 for a w/o emulsion 8

why do we want to match the HLB value of the emulsifier to that of the oil

it results in a superior product that has better stability WHILE USING THE MINIMUM QUANTITY OF EMULSIFIER

name the 3 types of emulsifiers available

natural products finely divided solids synthetic compounds

____ and ___ are NATURAL emulsifiers and generally used for which emulsions?

gums obtained from trees (acacia, tragacanth) gelatins used for oral o/w emulsions

name a type of finely divided solid emulsion. what kind of emulsions do they form

clays when added to water, form o/w when water volume is greater than the oil

true or false bentonite can also form w/o emulsions

TRUE

name 3 types of synthetic surfactants

anionic cationic nonionic

what kind of emulsions do synthetic surfactants form

form o/w or w/o are used in TOPICAL PREPARATIONS

TRUE OR FALSE anionic and cationic surfactants are compatible

FALSE The charges neutralize each other and they are incompatible

true or false emulsifiers should be stable and not deteriorate during storage

true

besides being stable, name 4 other requirements for emulsifiers

non toxic physically stable (taste, odor) chemically stable therapeutically compatible with the drug and other ingredients

how can acacia be administered? what is the significance of this?

can be administered orally but NOT iv this shows that emulsifying agents are selected based on the intended route of administration as some toxic effects DIFFER dpeending on the route of administration

what is microcrystalline cellulose used for

to increase viscosity and prevent the settling of the dispersed phase

___________ are used in TOPICAL emulsions as thickening agents to stabilize emulsions

high molecular weight alcohols like stearyl alcohol and cetyl alcohol

the _____, _____, and _______ properties of the API must be reviewed before selecting excipients

physical, chemical, and pharmaceutical properties

besides physical, chemical, and pharmaceutical properties of the API, what else is important in the selection of the appropriate dose volume of the designed product

the knowledge of the target population and the recommended dose for the indication

when the type of emulsion and the HLB required is determined, what is selected?

an emulsifier

what is an important consideration about the container of an emulsion

there must be adequate free space for shaking

emulsions mask.....

the disagreeable taste and odor of drugs

what can you say about drug absorption and emulsions

drug absorption is enhanced through GI tract

--------- are injected IV in the form of emulsions

nutrient oils

___________ preparations can be formulated in the form of emulsions give 4 examples

topical cold creams shaving creams turpentine liniment benzyl benzoate

how is a sustained release emulsion prepared

water soluble antigens and some drugs are formulated as water in oil type emulsions for IM DEPOT INJECTION PURPOSES (sustained release)

what is creaming? what kind of instability is it?

physical instability movement of dispersed droplets either upward or downward (depending on the density of the phases). results in a non-homogeneous product -- has 2 regions: emulsion and cream

the movement in creaming is based on....

stokes law

true or false creaming is irreversible

FALSE reversible and shaking an redisperse the droplets unifmrly

how can creaming be decreased

by reducing the droplet size and increasing the density of the external phase

the rate of creaming increases when....

when the droplets aggregate to large droplets but do not fuse (flocculate)

as mentioned, the rate of creaming is increased when the droplets aggregate but do not fuse (flocculate) how can creaming in this way be prevented

an appropriate surfactant can be used to control the electrical charge on the aggregates and prevent creamins

define coalescence

the fusion of droplets to larger globules

what does coalescence lead to?

cracking irreversible separation of the smulsion into 2 layers

true or false when an emulsion cracks, the product must be reformulated as the emulsion CANNOT be reformed upon shaking

true

name 3 causes of cracking

-poor technique -incompatiblity or degradation of the emulsifier -change in storage temperature

what is it called when an o/w emulsion concerts to a w/o emulsion and vice versa

phase inversion occurs when dispersed phase is greater than 74% of the total volume