Suspensions Flashcards
What is a pharmaceutical suspension?
Coarse dispersion
What does a suspension contain?
finely divided insoluble particulate material suspended in a
liquid or semisolid medium (continuous phase or vehicle)
What is the criteria for a suspension? (3)
PMS
Particles are uniformly distributed
Minimal solubility in the continuous phase
Size is from 1-100um
What are the advantages of suspensions?
Deliver poor water soluble drugs
Chemical stability
Palatability
Sustained release
What are the disadvantages of a suspension?
Settling over time leading to lack of uniformity of the dose
Manufacturing difficulties
What are the components of a suspension?
Hydrophilic solids
Hydrophobic solids
External phase (Dispersion medium and vehicle)
What are the external phases that can make up 100% of the medium?
Water
Simple Syrup
Cherry syrup
What are the non-polar liquids of the external phase of suspensions?
Oils
Fatty esters
Hydrocarbons
What are some other ingredients added to suspensions? (2)
They do something
Flocculating agents
Viscosity modifiers
Do electrolytes decrease or increase Zeta potential?
Decrease
Do ionic surfactants decrease or increase Zeta potential?
decrease
Why are polysaccharides used only for extemporaneous compounding?
Susceptibility to microbial growth
What are the 3 polysaccharides we should know?
Acacia gum
Tragacanth
Alginates
What do semi-synthetic cellulose derivatives do?
Increase the range of viscosity
What are the water soluble cellulose derivatives we should know? (Viscosity modifiers)
Methylcellulose
Microcrystalline cellulose
What are the hydrated silicates we should know?
Bentonite
Just increases viscosity
WHat are acrylic acid polymers?
HMW cross linked polymers of acrylic acid form gels in neutralized aqueous dispersions
What is the acrylic acid polymers we should know?
Carbopol, enhance viscosity and trap particles
What is colloidal silicon dioxide?
Aerosil
Fluffy white powder used as either a suspending or thickening agent or a tablet/capsule diluent
Helps with thickening of formulation in tablet capsule diluent
What are the properties of a ideal suspending agent/viscosity modifier?
Dissolved/dispersed without special techniques
Uniformly incorporated
Loosely packed system
no effect on Bioavailability
no Incompatibilities
Stability
What are the suspension types? (5)
Oral suspensions
Topical suspensions
Parenteral suspensions
Sterile topical suspensions
Cosmetics
What are deflocculated suspensions?
Dispersed particles are small discrete units and have slower gravitational settling
Very difficult to redisperse because the small particles settle and no liquid is between them
What are flocculated suspensions?
Particles settle as flocs and the rate of sedimentation is rapid, but liquid is trapped hence it becomes easy to redisperse
Is the supernatant clouding or clear in flocculated suspensions
Clear
Is the supernatant clouding or clear in deflocculated suspensions
cloudy
What are the physical properties of a well-formulated pharmaceutical suspension?
Resuspendable
Suspended long enough to remove a dose
Sufficiently small
Suitable viscosity
What are the properties of a high zeta potential?
Have greater repulsive forces > Attractive forces
The system is dispersed or deflocculated hence it will cake
What are the properties of a low zeta potential?
Have greater attractive forces > repulsive forces
System will be flocculated (Hence prevents caking)
What is the reason and solution for caking
High zeta potential (Deflocculated) solute is flocculate
What is the reason and solution for Crystal Growth
Partial solubility, temp fluctuation
Select the insoluble form of the drug, keep it at constant temp, and narrow size distribution
What is the reason and solution for Poor redispersibility
Caking, High viscosity, deflocculated suspension
Flocculate, keep viscosity optimal
What is the reason and solution for cap lock
Sugar in the formula
Use a mix of sugar and artificial sweetener
What is the reason and solution for settling
Low viscosity, large particles
Increase viscosity, reduce particle size
What is the reason and solution for Flavour changes
Incompatibility
Select another flavour
What is the reason and solution for colour changing
Incompatibility, too much air incorporated
Solve incompatibility, avoid air bubbles
What are most pharmaceutical substances?
Hydrophobic solids
What are hydrophobic solids?
Not wetted by water but wetted by oils
What are hydrophilic solids
Readily wetted by water
What are the only polar liquid solvents you can go up to 100%
Water, Simple syrup, cherry syrup
What are the external phase non-polar liquids that we can use up to 100%
Oils
Fatty esters
Hydrocarbons
What are the external phase structured vehicles we should know?
ATCMC
Acacian
Tragacanth
Carbopol
methyl cellulose derivatives
Colloidal silicon dioxide
What is thixotropic
Gets solid when standing, but liquid when moving
What is Zeta potential>
It is the particle charge
Does larger zeta potential on particles lead to flocculation or deflocculation?
deflocculation (More dispersed)
Decreases in zeta potential
decrease deflocculation (Hence making particles more clumpy and more flocculated)
What are deflocculated suspensions usually used/made
Usually pharmacy compound for short term
What does sodium lauryl sulfate <1% do?
Neutralized static electricity
compounding tip
In a suspension the particles have a ___ solubility in the continuos phase.
minimal
Why are suspension not used for parenteral administration?
Due to the settling and sometimes thixotropic effects of the suspension
What are some sweeteners one could use for a suspension?
Sugar, lactose, dextrose
How can we decrease Zeta potential
Adding electrolytes, ionic surfactants
Does polymeric flocculating agents effect Zeta potential?
No, instead if increases viscosity
Which type (Flocculated or Defloculated) is not recommended for storing over a long period of time?
Defloculated due to caking
What does Magnesium stearate <1% do?
Enhances flowability
What does Sodium Lauryl sulphate do <1%?
Neutralized static electricity
