Suspensions (exam 2) Flashcards
dispersed system
liquid preperation containing undissolved or immiscible drug in a vehicle
phases in a suspension
dispersed phase
dispersing phase/medium (vehicle)
label for suspensions
shake well
coarse dispersions
contain large particles
ex: suspensions, emulsions
fine dispersions
contain small particles
ex: magmas, gels
suspensions are liquid preparations containing _________________ in a liquid phase in which particles are ___________________
solid drug particles dispersed
not soluble
pharmaceutical suspensions has to possess
therapeutic efficacy
chemical stability
permanency of preparation
esthetic appeal
routes of administration for suspensions
oral
topical
ophthalmic
parenteral
reasons to formulate a suspension
when a drug is insoluble
when a drug is unstable in solution
when the taste is bad, needs to be overcome
suspensions contain
large solid drug particles
sedimentation
particles tend to settle, redisperse upon shaking
__________________ is very important to the accurate administration of doses
uniform redistribution
caking of suspension
rigid cohesion of particles that resists breakdown upon shaking
what can prevent caking?
how?
flocculation
enhances particle dispersability
what type of particles produce more stable suspensions?
barrel shaped particles
flocs resist complete settling, but flocculated particles ________________ than fine particles
settle faster
stokes equation says sedimentation rate can be decreased by
reduce the particles size (dispersed phase)
increase the viscosity of the suspension (dispersion medium)
zeta potential
voltage difference between ions in tightly bund layer and electroneutral region
the magnitude of the zeta potential gives an indication of
the stability of the dispersion system
suspension with zeta potential between -30mV and +30mV
unstable
suspension with zeta potential more than +30mV or less than -30mV
stable
micropulverization
for oral and topical solutions
mill and beaters produce fine drug power
grinding
for parenteral and ophthalmic solutions
rotating hammers/pins produce very fine particles
spray drying
cone shaped apparatus rapidly dries and produces very very small particles
compounding mechanism to decrease particle size
trituration
suspensions for neonates should not include
preservatives
alcohol
color
flavors
which type of powder requires a wetting agent? and why?
hydrophobic powders
not wet by water
how does wetting agents work?
disperse air in the particles
disperse particles
allow penetration of dispersion medium into powder
examples of wetting agents (2-5%)
alcohol
glycerin
propylene glycol
surfactants
suspending agents are added to
thicken the dispersion medium
examples of suspending agents (1%)
carboxymethylcellulose
methylcellulose
microcrystalline cellulose
polyvinyl pyrrolidone
examples of flocculating agents
clays
electrolytes
nonionic surfactants
ionic surfactants
why is a portion of the vehicle used to wash mixing equipment?
to ensure correct drug concentration in the suspension
suspensions are physically
unstable systems
beyond use date when stability is not known
14 days
packaging and storage of suspensions
wide mouth containers
adequate airspace above liquid
tight, light resistant container
protect from freezing and excessive heat
stored in fridge
types of suspensions
ready to use form of suspensions
dry powders for oral suspension
extemporaneously compounded suspensions
usual adult dose of an oral suspension is
5 ml (1 tsp)
pediatric dosing of suspension is
dose calibrated number of drops
