Suspension Flashcards
Define Suspensions
a coarse dispersion containing
finely divided insoluble particulate material suspended in a
liquid or semisolid medium
What are the criteria for suspensions (particles)
are uniformly distributed
have minimal solubility in the continuous phase
What are the criteria for suspensions (size)
the size distrubution of the particles ranges from 1-100 um (diameter)
What is the size (um) of fine dispersion?
1-50 um
What is the size (um) of coarse dispersion?
50-100 um
List some of the advantages of suspensions?
Deliver poor water-soluble drugs
Suitable for patients with difficulty in swallowing a tablet or capsule
Palatability (masking taste)
Chemical stability (hydrolysis,…)
Sustained Release
Can be given for both systemic (antibiotics) and local therapeutic effects (activated charcoal to adsorb excess GI fluid)
What are some disadvantages of suspesions?
Physical instability, settling over time results in lack of uniformity of the dose
Manufacturing Difficulties
List some requirement of acceptable suspensions
Should not precipitate rapidly
Redispersed quickly by shaking
Correct viscosity to pour from the bottle/flow through an administration needle
For topical formulations sufficiently fluid to spread over the skin
What are the two types of internal phase?
hydrophilic solids
hydrophobic solids
List some examples of hydrophilic solids in internal phase
clays (kaolin, talc, magnesium aluminum silicate)
hydroxides and oxides of calcium, magnesium, zinc, aluminum & titanium
List some examples of hydrophobic solids in internal phase
most pharmaceutical substances: charcoal, sulfur, aspirin, phenobarbital
List some factors that are used for selection of external phase (medium)
safety
density
viscosity (for stability)
taste
stability
What types of external phase are used in suspension?
polar liquid
non-polar liquid
structured vehicles
List some examples of polar liquids used in suspensions
water
alcohol
polyols (glycerin)
glycols (propylene glycol)
simple syrup
cherry syrup
sorbitol solution
List some examples of non polar liquids used in suspensions
oils
fatty esters
hydrocarbons
List some examples of structured vehicles used in suspensions
acacia
tragacanth
carbopol
methylcellulose derivatives
colloidal silicon dioxide
T/F Is water the only external phase that can be used up to 100%
False non polar can too
What is the percentage that polymer can be in the final composition for structured vehicles?
0.5-5%
What is the percentage can be used for the following?
water
simple syrup
cherry syrup
up to 100%
50-100%
50-100%
What are the two roles that structured vehicles can be based on concentration?
protective colloids at low concentration
viscosity-inducing agents at higher concentration
Describe thixotropic behavior
by stirring or shaking will decrease viscosity
T/F Structured Vehicles can be used for parenteral administration
False they can not as there is an issue with syringeability
What other important ingredients in suspensions?
suspending (flocculating) agents
viscosity modifiers
What are the characteristics important for suspending agents?
electrolytes
ionic surfactants
polymeric flocculating agents
What are the characteristics important for viscosity modifiers?
polysaccharides
water soluble cellulose derivatives
hydrated silicates
acrylic acid polymers
colloidal silicon dioxide
What does electrolytes do?
They help to deflock the particles
by reducing the zeta potential
(stop them from clumping)
What does the ionic surfactants do?
they reduced the capable of zeta potential
What does polymeric flocculating agents do?
form a gel like network to cross link the suspended particles
also increase viscosity
What is polysaccharides used for? Why?
only for extemporaneous compounding
because of their increased susceptibility to microbial growth
List some examples of polysaccharides used for suspensions
acacia gum
tragacanth
alginates
How do water soluble cellulose derivatives work in suspensions?
make greater viscosity ranges available by combining agents in specific proportions
List some examples of water soluble cellulose derivatives
methylcellulose
microcrystalline cellulose
List an example of hydrated silicates
bentonite
How do acrylic acid polymers?
HIgh molecular weight cross linked polymers of acrylic acid form gels in neutralized aqueous dispersions
Give an example of acrylic acid polymers
carbopol
Explain colloidal silicon dioxide
fluffy white powder used as either a suspending/thickening agent or a tablet/capsule diluent
List the suspension types based on pharmaceutical application
oral
topical
parenteral
sterile topical
cosmetics
List the suspension types based on physical structures
deflocculated
flocculated
List some properties of an ideal suspending agent modifier
readily dissolved/dispersed without special techniques
readily and uniformly incorporated
ensures formulation of loosely packed system
no effect on bioavailability of the drug
no incompatibilities
stability over wide pH range
Examples of oral suspensions
antibiotics
antacids
radiopaque suspensions
Examples of topical
calamine lotions
Examples of parenteral suspensions
I.M
S.C
intralesional
intraarticular
Examples of sterile topical suspensions
ophthalmic suspensions
List some properties of well formulated suspensions
must be easily resuspendable
after shaking the dispersed phase is suspended long enough to remove a dose
particles should be sufficiently small to appear smooth
has suitable viscosity
List some properties of deflocculated suspensions
cloudy and slow to settle
caking at the bottom after long term of settlement
List some properties of flocculated suspensions
form loose aggregates (clumps)
particles settle as flocs
rate of sedimentation is relatively rapid
“fluffy”
What are some compounding tips?
dust masks should be worn
aerosolizing powders make them easier to work with, or adding a few drops of alcohol, water or mineral oil
Define high zeta potential
repulsive forces > attractive forces
system will be dispersed or deflock
upon settling the suspension will cake –> difficult to resuspend
Define lower zeta potential
attractive forces > repulsive forces
system will be flocc (prevent caking)
What are the three factors of uniform dispersion of deflocculated particles?
incorporation of structured vehicle
addition of flocculating agent
addition of flocculating agents
Why is incorporation of structured vehicle important?
deflocculated suspension in structured vehicle as final product
Why is addition of flocculating agent important?
flocculated suspension as final product
Why is addition of flocculating agents important?
flocculated suspension
incorporation of structured vehicle
flocculated suspension in structured vehicle as final product
