Suspension Flashcards
Suspensions have _____ dissolution/absorption than tablets
faster
Suspensions have _______ dissolution/absorption than solutions
slower
What are the three kinds of delivery routes in suspensions?
- Oral
- Externally applied
- Parenteral
What are the two classifications of suspensions?
- Colloidal
2. Coarse
What are the particle sizes in colloidal suspensions?
<1 micron
Which classification of suspensions are always treated as suspensions?
Coarse
Which classification of suspensions are treated as either suspensions or solution depending on the case?
Colloidal
What are the particle sizes in coarse suspensions?
> 1 micron
Which classification of suspensions settle under gravity?
Coarse
Which classification of suspensions typically do not settle?
Colloidal
A good pharmaceutical suspension has _____ sedimentation rate
slow
Sedimentation rate is derived from ideal situations where particles are _____ and ____
uniform, spherical
Sedimentation rate is derived from ideal situations where suspension is _______
dilute
Sedimentation rate is derived from ideal situations where no _______ during particle settling
turbulence
Sedimentation rate is derived from ideal situations where no particles ________ with each other
collide
Sedimentation rate is derived from ideal situations where no _____ and _____ interactions between particles and medium
chemical, physical
What is Stokes equation?
Rate of sedimentation =
d^2(particle density - medium density) * gravitation constant /(18 * viscosity of medium)
Stokes equation does / does not apply directly to pharmaceutical preparations
does not
T / F Suspensions will not always settle over time
False, eventually settle
What happens if density of medium is greater than density of particles?
Particles float to surface
Why is having particles floating to the surface a bad thing?
Although there is not settling, it makes dosing difficult
What happens if density of particles is greater than density of medium?
Particles settle
What happens if density of particles is MUCH greater than density of medium? What the problem with it?
Particles settle very fast
May be difficult to dose accurately
Why is having particle sizes too small a problem?
Settles slowly, but forms hard cake
Why is having particle sizes too large a problem?
Will settle fast, but will be easy to re-disperse
Vehicle vs particle, which is easier to adjust?
Particles
How easy is ti to re- distribute hard cakes?
It’s not easy, it is to be avoided
What is flocculation?
The process by which particles settle fast in a very loose/easy to redisperse mass
What can you add to promote flocculation?
- Clays in oral suspension
- pH adjustment / electrolytes
- Surfactants
How does adding sufactants promote flocculation?
Wet particle surfaces + prevents them from sticking to each other
How does adjusting pH and electrolytes promote flocculation?
Promotes ionic interaction to form a structure
What kind of tension does surfactants bring to the lipophilic particle and the hydrophilic medium?
Interfacial tension
How much wetting agent should you use when preparing suspensions? Why?
As little as possible
Too much causes foaming, bad taste, dissolution of drug
In general, drugs are ____ stable in liquid than solid form
less
