Part 2 Flashcards
if we need to reduce the size of the particles, what kind of agent do we use?
if the particle size does NOT need to be reduced, what kind of agent do we use?
particle size doesnt need to be reduced = wetting agent
needs to be reduced = levigating agent
name 2 things that affect the bioavailability of drugs from suspensions
-dispersed powder
-dispersed vehicles
name 4 ways in which the dispersed powder affects the bioavailability of drugs from suspensions
-particle size
-particle shape
-surface characteristics
-polymorphism
how can the dispersed vehicle affect the bioavailability
if the medium is too viscous, the powder will diffuse very slowly out of the medium.
therefore, we don’t want the viscosity too high - only 1-2% methylcellulose
true or false
a suspension with smooth surface particles will have higher bioavailability than rough surface particles
FALSE
rough particles will have higher bioavailability bc dissolution rate is higher
at the oil-water interface (in the cause of suspensions - particle - water interface), what exists?
an electrical double layer
what is “e”
energy potential on the particle surface. represents the energy that comes from the surfactant itself
(we don’t really measure this – we measure zeta)
what can you say about the charge of the bulk solution in a suspension
it is electrically NEUTRAL
at a position very close to a solid particle in a suspension, is the zeta potential high or low?
very high. as you move further away from the particle and approach the bulk solution, the zeta potential decreases exponentially
2 particles are very far away from each other. as 1 particle approaches the other, does the zeta potential increase or decrease?
increase
particles with a very large contact angle are hydrophobic or hydrophilic
hydrophobic
the function of a wetting agent is to get rid of the air above the solid particles.
how is this helpful in a suspension?
helps the particles disperse in the medium
true or false
if a wetting agent is used, a levigating agent is not needed
true
zeta potential measures what part of a suspension
the mobile or diffuse portion of the double layer
(Fixed layer = around the solid particle)
define gels
gels are semisolid systems consisting of either –
-suspensions made of inorganic particles
-large organic molecules
interpenetrated by a liquid
name 4 advantages of gels
-semisolid
-easy to apply and remove
-high degree of clarity
-compared to ointments and creams, they have fast release of drug
which have faster release of drug – ointments/creams or gels?
gels have faster drug release
give an example of a gel and explain it in detail
Aluminum Hydroxide Gel, USP (BASIC)
it is an aqueous suspension of gelatinous precipitate (made of insoluble aluminum hydroxide and hydrated aluminum hydroxide, equivalent to about 4% aluminum oxide
neutralizes a portion of gastric HCl and is used to treat hyperacidity and peptic ulcers.
-this will remain in the stomach for local effects while a tablet would go to the small intestine
true or false
Aluminum Hydroxide, USP is an acidic drug
FALSE - basic. that’s how it can neutralize stomach acid
how can gels be classified
4 types:
-inorganic
-organic
-hydrogels
-organogels
true or false
inorganic gels are typically single-phase systems and organic gels are typically two-phase sytems
FALSE
inorganic gels are typically 2-phase
organic gels are typically single-phase
give 2 examples of inorganic gels
aluminum hydroxide gel
bentonite magma
gave 2 examples of organic gels
carbopol
tragacanth
explain what Carbopol is
frequently used in research
an organic, single phase system.
USED TO INCREASE THE VISCOSITY OF THE DISPERSED MEDIUM. the drug will dissolve in the water and then that water will integrate into the Carbopol structure