Dosage II Exam 1 Flashcards
A homogeneous molecular dispersion defines what liquid dosage form?
Solution
Oil in water or water in oil is an example of what liquid dosage form?
Emulsion
Solid in water or oil is an example of what liquid dosage form?
Suspension
What are the 3 liquid dosage forms we talked about in class?
Solution, emulsion and suspension
A mixture of sugar and water where the sugar dissolves completely would be considered what type of dosage form?
Solution
Small liquid droplets/particles suspended in solution would be an example of which liquid dosage form?
Emulsion
Small solid particles suspended in solution (e.g. milk) would be an example of which type of liquid dosage form?
Suspension
Suspensions and emulsions both have suspended agents within their solutions. What are the characteristics of the suspended agents that make these two liquid dosage forms unique?
A suspension has SOLID particle suspended in solution where an emulsion consists of LIQUID droplets/particles suspended in solution.
Homogenous or Heterogeneous?
Emulsion
Solution
Suspension
Emulsion = hetero Solution = homo Suspension = hetero
Solution contain _____ and therefore have a greater chance of contamination.
water
Because bacteria can grow in water part of a solution, in order to keep the nasties out the solution it needs ________.
antimicrobial agents
Enemas, injectables, nasal solutions, mouthwashes and juices are all examples of which liquid dosage form?
solution
Of solutions, emulsions and suspensions, which is the LEAST stable?
solutions
What is content uniformity?
Content uniformity is assurance that each sample taken from a batch is the same
List 3 advantages of a solution.
- ) Homogeneous - no problems with content uniformity
- ) Easy to manufacture
- ) Good bioavailability
For a solution where all the material is completely dissolved, assuming all ingredients are soluble, as long as you measure the volume correctly you will achieve _____ _____.
content uniformity
With solution, which part can you omit from ADME?
D
Active ingredient (API), solvent, buffer, preservative, antioxidant, chelating agent, and flavor ant are all components of which liquid dosage form?
solution
Most of the time a solvent is made up of ______. However, if material is not soluble in the above answer, what is the other solvent?
co-solvent
List 2 long lasting parenteral solvents.
water and vegetable oils
List 3 example of co-solvents
ethanol, glycerin, propylene glycol
What are the 2 main objectives (questions) in determining a buffer?
- ) How much buffer capacity the buffer has to have?
2. ) What pH does the buffer need to provide?
A _____ is a solution of a weak acid and a salt of its conjugate base.
buffer
In terms of a buffer, a weak acid removes added ______.
base (OH-)
In terms of a buffer, a salt removes added ______.
acid (H+)
What is the purpose of antioxidants in solution dosage forms?
Insures stability b/c oxidants will produce ROS which will compromise stability.
With a weak acid or salt you can establish a desired _____.
pH
Buffer capacity is maximum in what situation?
when pH = pKa
Write the Hendersen - Hasselbalch equation.
pH = pKa + log [A-] / [HA]
or
pKa = pH + log [HA] / [A-]
Write the Van Slyke equation.
Beta = 2.3 * C * Ka * [H3O+] / (Ka + [H3O+])^2
“C” in the Van Slyke equation is what….
Total buffer concentration….[A-] + [HA]
The ability of a buffer to resist a change in pH due to added OH- or H+ defines what?
Buffer capacity.
Beta in the Van Slyke equation will tell you …..
the amount of acid or base needed to change the pH
In terms of buffer capacity, in what situation would you need a lot of acid or base to change the pH?
high buffer capacity
In terms of buffer capacity, in what situation would you need only a small bit of acid or base to change the pH?
low buffer capacity
Matching:
High buffer capacity =
Low buffer capacity =
A.) Strong buffer against acid or base
B.) Weak buffer against acid or base
High buffer capacity = A
Low buffer capacity = B
If a drug is most stable at pH = X, then the buffer should be pH = _____.
X
All ____ ____ ionize in water and have buffering capacity.
weak acids
Which equation will give you the ratio of acid and salt?
Hendersen-Hasslebalch
Which equation will provide how much buffer capacity you need?
Van Slyke
In terms of pH, how could you minimize irritation with parenterals, opthalmic or nasal dosage forms?
adjust the pH to be the same as the pH of the body fluid.
If the pH cannot be matched with the body fluid for parenterals, opthalmic or nasal dosage forms, what are some techniques you can use to minimize irritation?
- minimize buffer capacity
- minimize volume
- administer slowly
For external formulations a high buffer capacity is ok, but for injectable solutions a high buffer capacity is not desirable. Something with a pH = 3 will sting during and for a long time afterwards.
Understand
A buffer contains 0.1 M sodium formate and 0.1 formic acid. 0.05 M of sodium hydroxide was added. The Ka of formic acid is 1.77x10^-4 (pKa = 3.75).
- What is the initial pH of the buffer?
- What is the buffer capacity?
- What is the pH after the addition of sodium hydroxide.
- 3.75
- 0.115 M
- 4.23
Design a buffer for a penicillin solution that is most stable at pH 6.5. A buffer capacity of 0.1 is required.
[HA] = 0.078M [A-] = 0.098
To protect patients from pathogens and maintain potency and stability of dosage form is the purpose of what?
antimicrobial preservatives
Matching:
- ) Need not be sterile but should not contain pathogens. FDA limits the number of organisms (e.g., E. coli) to be less than 100 per mL. Need preservatives for multiple dose packages.
- ) Must be sterile, single dose, no preservative needed.
- ) Must be sterile, must contain a preservative if packaged in multiple dose container.
- ) Less likely to carry bacteria than liquid dosage forms. Pathogen contamination is still a concern (e.g., Salmonella). Test raw materials and be sure that the manufacturing facility is clean.
- ) Must be sterile, may contain up to 10 doses, need preservative to kill microorganisms introduced during use.
A.) Ampules B.) Multiple Dose Vials C.) Opthalmic Solutions D.) Oral Liquids E.) Oral Solids
1D
2A
3C
4E
5B
What is the mechanism of action for antimicrobial preservatives?
The absorb to the bacterial membrane due to lipid solubility or electrostatic attractions and disrupt it.
List some examples of antimicrobial preservatives that absorb due to lipophilicity.
Alcohols, acids and esters
List some examples of antimicrobial preservatives that absorb due to electrostatic attractions.
Quaternary ammonium compounds
Effective in low concentrations against a wide variety of organisms, soluble in formulation, non-toxic and stability are all requirements for what?
ideal antimicrobial preservatives
The bacterial membrane is _______ (hydro/lipo-philic) and has a net _____ surface charge.
lipophilic / negative
List 3 types of liquid dosage forms.
Solution, emulsion and suspension
_______, a pharmaceutical preservative, requires greater than 15%, has limited oral products and may be lost due to volatility.
Ethanol
______, a pharmaceutical preservative, has a local anesthetic action and a burning taste (therefore not used orally), is water soluble, stable over a wide pH range and widely used in parenterals.
Benzyl alcohol
______, a pharmaceutical preservative, has a campor-like odor and taste (therefore not used orally), used in parenterals, ophthalmics, is volatile and can be lost through rubber stoppers and plastic containers.
Chlorobutanol
As a pharmaceutical preservative, ______, are only active in their unionized (______ - soluble) form.
acids / lipid
What are the two weak acids that can be used as an oral pharmaceutical preservative.
Benzoic acid and sorbic acid
Benzoic acid (pKa 4.2) and sorbic acid (pKa 4.8) are effective as oral pharmaceutical preservatives. In what situation(s) might they loose their effectiveness?
When the pH of the system is greater than their pKa value
1 of the 2 acids used as oral pharmaceutical preservatives and is excellent for molds and yeast.
Sorbic acid
Esters of p-hydroxybenzoic acid are also called…
parabens
Parabens are widely used _____. The do not ionize, but rather ______ rapidly at pH values greater than ____.
orally / hydrolyze / 7
Lipophilic parabens are best against….
mold and yeast
Lipophobic parabens are best against….
bacteria
List some examples of lipophilic parabens…
propyl and butyl parabens
List some examples of lipophobic paragons…
methyl and ethyl parabens
Paraben disadvantages:
Low ______
Cause _____ sensitization when used in dermatological products.
solubility
skin
Draw the general structure of a paraben….and then methylparaben and ethylparaben…
X
Benzalkonium chloride (Zephirin) is what kind of pharmaceutical preservative?
Quaternary ammonium compound
Cetyltrimethylammonium chloride (Cepryn) is what kind of pharmaceutics preservative?
Quaternary ammonium compound
What are the 4 pharmaceutical preservatives we talked about in class?
alcohols, acids, parabens and quaternary ammonium compound
Quaternary ammonium compounds, as pharmaceutical preservatives, are used widely as ________, are very _____ soluble and _____ killing.
ophthalmics / water / fast
The + charge on the quaternary ammonium compounds enable them to be ____ killers of bacteria. However, that + charge also renders them ______ because they can lose activity by binding to proteins or anything else with a negative charge.
fast / incompatible
Benzalkonium chloride and cetyltrimethyammonium chloride have a ____ charge.
positive
Only the _______ species of weak acids are effective as a preservative. Add more total weak acid when pH is _____ pKa in order to have an effective concentration of unionized species.
unionized / above
Drug substances are ______ (more or less) stable in aqueous media than solid dosage forms.
less
What 4 main rxns can occur between ingredient-ingredient interactions or container-product interactions.
acid-base
acid or base catalysis
oxidation
reduction
Automatic reaction with oxygen without drastic external interference defines what?
auto-oxidation
Vitamins, essential oils, fats and oils can all be…
oxidized
_____ is initiated by heat, light, peroxides, metals (copper or iron) –> free radicals –> react with oxygen –> more free radicals
Oxidation
List 3 types of antioxidants.
Free-radical scavengers, reducing agents, chelating agents
List some examples of free radicals scavengers.
Propyl, octyl, dodecyl esters of gallic acid, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tocopherols, vitamin E
What does a free-radial scavenger do?
Retards or delays oxidation by rapidly reacting with free radicals.
How is a reducing agent an antioxidant?
It has a lower redox potential as compared to the drug, so it will be more rapidly oxidized compared to the drug.
List some examples of reducing agents.
Sodium bisulfite, ascorbic acid
What does a chelating agent do that makes it an antioxidant?
removes trace metals
List some examples of chelating agents.
EDTA and citric acid
A system of two immiscible liquids in which one is dispersed as droplets (a liquid-liquid mixture).
Emulsion
In pharmacy, emulsions has two phases, what are they?
dispersed phase and continuous phase
Which of the emulsion phases determines the organoleptic properties (taste, smell, fell)?
continuous
Can an oil be injected intravenously?
NO. Not by itself anyway. If its part of an emulsion it can be, but not by itself.
Which makes up the greater % of the emulsion: the dispersed or continuous phase?
continuous
If water is the _________ phase then the emulsion feels, smells and tastes like water. If oil is the ________ phase, then the emulsion feels, smells and tastes like oil.
continuous / continuous
An O/W oral application of an emulsion will mask the taste of the _____. List an example of an oral application of O/W.
oil / mineral oil as a laxative
What are two advantages of a O/W oral application of an emulsion?
- ) an O/W will mask the taste of the oil (e.g. mineral oil as a laxative
- ) it will enhance the absorption of an oil (vitamin A and D, cod liver oil)
An emulsion can also be used as an external application. Give example of both O/W and W/O.
O/W = water-washable, vanishing cream
W/O = For cleansing skin, cold cream
An intravenous lipid emulsion is (O/W or W/O)?
O/W
Give an example of intravenous lipid emulsion.
parenteral nutrition (TPN)
In regards to intravenous lipid emulsion, the smallest capillaries are ____ microns. It is critical that the droplet size is less than _____ microns to avoid _____.
5 / 1 / embolisms
Emulsions are ________ ________ and will crash out if not stabilized.
thermodynamically unstable
Water molecules act with other water molecules. Oil molecules act with other oil molecules. If you mix them together, they may looked mixed for a minute, but they will begin to separate and go back to acting with their own groups (water with water and oil with oil). This phenomena is called….
interfacial tension
Thermodynamically, emulsion is a (high or low) energy liquid?
high
The _____ the interfacial tension is the more comparable the two liquids are with one another. The _____ the difference between two liquids, the greater they tend to separate from one another.
smaller / greater. The greater the difference the more quickly they will separate also.
Liquid - liquid interface = what kind of tension
Liquid - air interface = what kind of tension
interfacial tension
a special kind of interfacial tension called surface tension.
If waters BP is 100 and ethanols BP is 70, which has the greater surface tension?
Water. It takes more energy to break the intermolecular forces.
The stronger the intermolecular force in a bulk phase, the higher the _____ ______.
Interfacial tension
In an emulsion, the two phases don’t like to hang out with each other…UNLESS…we have an….
emulsifying agent
Why are emulsifying agents added to emulsions?
for stability
List three types of emulsifying agents:
Surface active agents (AKA surfactants)
Hydrophilic colloids
Finely divided solid particles
A _____ is amphiphilic. What does it mean to be amphiphilic?
surfactant
amphiphilic has a hydrophobic end and a hydrophilic end (e.g. polysorbate 60)
Think about how a surfactant would orient itself in a liquid-liquid interface or a liquid-air interface.
Oil and water don’t mix well. But if there was a ______ (specific emulsifying agent) included with them, it would act as a stitch that would lock them together because of its amphiphilic character.
surfactant….hydrophobic end would go in the oil and the hydrophilic would go in the water….joining the two phases together like a zipper….think about it, a surfactant has properties of both liquid phases.
A good surfactant will have and ______ end and a ______ end.
hydrophilic and hydrophobic
Given figures and structures, but able to distinguish a surfactant.
will have a hydrophobic end and hydrophilic end. Long carbon chains are lipophilic (hydrophobic) and the polar head group will be hydrophilic.
T or F: A surfactant can be anionic, cationic, zwitterionic and nonionic?
T
What does HLB stand for?
Hydrophile - lipophile balance.
Not all surfactants are the same. _____ is a way to classify the surfactants.
HLB
The quantitative measure to determine if the surfactant is closer to oil or water.
HLB
The higher the HLB value, the closer the surfactant is to ______ (water/oil).
water…and visa versa…the lower the number, the more lipid like it is.
In which emulsion would you use an oil like surfactant? O/W or W/O Why? What HLB quantity would you assume…high or low?
W/O
The surfactant works best if it closely matches the continuous phase.
low
In which emulsion would you use a water like surfactant? O/W or W/O Why? What HLB quantity would you assume…high or low?
O/W
The surfactant works best if it closely matches the continuous phase.
high
The higher the HLB, the more the surfactant is like ______. (water or oil)
water
HLB = 4 vs. HLB = 14….match with oil and water
HLB = 4 = oil HLB = 14 = water
If you had a W/O emulsion, would you use a surfactant with a high or low HLB?
low
If you had a O/W emulsion, would you use a surfactant with a high or low HLB?
high
If you don’t know if the emulsion is O/W or W/O but you can can figure the HLB, what would a high HLB suggest about the emulsion and what would a low HLB suggest about the emulsion?
a high HLB would suggest that the emulsion is more water like and water is probably the continuous phase = O/W
a low HLB would suggest that the emulsion is more oil like and oil is probably the continuous phase = W/O
Prepare 1 L of O/W emulsion of an oil having an HLB of 12. The total surfactant is 1% of the formula. Calculate how much span 80 (HLB 4) and tween 80 (HLB 15) are required.
- 7 g span80
7. 3 g tween80
Draw an emulsion droplet
x
Draw a micelle.
x
At what point do micelles form?
at the CMC critical micelle concentration
As the concentration of the surfactant increases above a critical concentration, cmc, the surfactant molecules self-associate into small aggregates called….
micelles
Surfactant concentration and surface tension have what type of relationship?
inverse
_____ is tension between 2 liquids.
____ is tension between liquid and vapor (air)
interfacial tension
Surface tension
T or F: All surfactants are emulsifiers and all emulsifier are surfactants.
F. All surfactants are emulsifiers, but there are 3 type of emulsifiers …surfactants, hydrophilic colloids and finely divided solid particles…therefore all emulsifiers are not (only) surfactants.
Hydrophilic colloid doesnt care about the thermodynamics of the two phases and doesnt make them more compatable and therefore does not decrease the tension between the two phases, instead it puts a barricade between the two phases. Oil and water still hate each other…but what a hydrophilic colloid does is surround the oil so that they can’t join up and separate. HC do not reduce the ST but still act as an emulsifier.
x
Hydrophilic colloids (polymer) surround the oil droplet and in case it within the polymerare hydrophilic
x
Hydrophilic colloids only dissolve in water so they are only good for O/W emulsion.
x
Emulsification is the process by which a lipid mass is converted to a number of small lipid droplets. The process of emulsification happens before the fats can be absorbed by the intestinal walls.
X
What are the 6 components of a solution?
- ) API
- ) solvent
- ) buffer
- ) preservative
- ) antioxidant or chelating agent
- ) flavor or sweetener
List two advantages of oral O/W emulsions.
will mask the taste of oil and enhance absorption of an oil
What are the 4 categories of surfactants?
Anionic, Cationic, Zwitterionic and Nonionic
If you have an HLB between 0 - 20, what category of surfactant would you have?
And the lower they are, the greater ____ solubility.
HLB > 10 = ____ soluble.
anionic / lipid / water
If the emulsion is W/O, use a(n) ______-like surfactant.
oil
If the emulsion is O/W, use a(n) ______-like surfactant.
water
What does cmc stand for?
critical micelle concentration
How/when are micelles formed?
when the concentration of surfactant increases past the cmc, the surfactant molecules self associate and aggregate into micelles.
The center of the micelle represents a lipid-like region that is capable of dissolving ______ drugs.
water-insoluble
Surface active agents with HLB > 10 will be in what type of emulsion? W/O or O/W
O/W
Surface active agents with HLB < 10 will be in what type of emulsion? W/O or O/W
W/O
Hydrophilic colloids are only used in which type of emulsion? W/O or O/W
O/W
If the angle between the surface and the finely divided solids is > 90 degrees, that signifies the surface and FDP are _____ (compatible or non compatible) and therefore _____ (hydrophilic or hydrophobic) which indicates a(n) _____ emulsion?
non-compatible / hydrophobic / W/O
If the angle between the surface and the finely divided solids is
compatible / hydrophilic / O/W
Hydrophilic colloids form a multimolecular film at the interface and increase the _____ of water.
viscosity
T/F: Hydrophilic colloids lower the interfacial tension.
F
Acacia, tragacanth and gelatin are all examples of what?
hydrophilic colloid
1.) The phase volume ratio is made up of what?
- ) 0 - 26% =
- ) 26 - 74% =
- ) 74 - 100% =
1.) volume of the oil phase / total volume of the emulsion
- ) O/W only
- ) either O/W or W/O
- ) W/O only
What are the 3 common instability factors of an emulsion?
creaming, coalescence and phase inversion
What equation is associated with creaming?
Stokes Law
Clinical applications of emulsions
x
Understand the molecular basis of interfacial tension and how surfactants alter the interfacial tension
x
Understand the role of interfacial tension have in the production and stability of an emulsion
x
Understand the mechanism by which surfactants, hydrophilic colloids and finely divided solids act as emulsifying agents
Surfactants have a hydrophobic end and a hydrophilic end. They hydrophilic end will interact with the water phase and the hydrophobic end will interact with the oil phase and act as a zipper and hold both phases together by lowering the interfacial tension. We can use the HLB equation to determine the relative amounts of contributions of the hydrophilic and hydrophobic regions of a surfactant.
Hydrophilic colloids are used in O/W emulsions only because they only dissolve in water and not in oil. They form a multimolecular film at the interface and increase the viscosity of water. and unlike surfactants, hydrophilic colloids do not lower the interfacial tension.
Finely divided solid particles are particles less than a micron that can absorb at the interface and form a film of particles.
Understand the basis of physical instability of emulsions
Creaming: occurs because the two phases typically have different densities. And the oil phase, in this instance, has a small density than water and they try to float. Stokes Law eq tells you how fast creaming will occur. V in the Stokes Law eq is the velocity of sedimentation. If V comes out to be neg (-), then that means the particles will float. V will be big if the particle size is big or the difference between the densities of the dispersed phase and continuous phase is large. Densities of any two phases are almost always different so creaming will almost always happen at some degree.
- Emulsions can cream, that’s generally fine, all they need to do usually is shake it up again. But if it starts to coalescence, thats bad.
Coalescence: Small droplets combine to make big droplets. Irreversible, cannot be fixed. Bioavailability is increased when droplets are small, a large droplet (i.e. coalescence) decrease the bioavailability.
Phase inversion: If you don’t use the right type of water, it can change surfactant from High HLB to Low HLB, i.e. changes from W/O to O/W. Easy to solve this problem, don’t use tap water to make emulsion.
Be able to predict the type of emulsion by inspecting the formula
Predicting O/W or W/O:
When HLB > 10 = O/W When HLB < 10 = W/O Hydrophilic colloid only in O/W Finely divided particle - look at angle < 90 degrees = O/W > 90 degrees = W/O
If you know the volume %, you can make assumptions too: VOL OIL PHASE / TOT VOL OF EMULS = 0 - 26% = O/W only 26 - 74% = either W/O or O/W 74 - 100% - W/O only
Know the typical components of an emulsion and how to manufacture an emulsion
FYI, we do not shake in pharmaceutical production, we run it through a colloid mill or homogenizer.
- ) Dissolve all water soluble ingredients in water.
- ) Mix all oil-soluble ingredients in oil. (heat if necessary to melt)
- ) Heat both solutions to the same temperature.
- ) Mix both solutions together.
- ) Cool slowly.
- ) Pass through a colloid mill or homogenizer.
Know why you would select a suspension dosage form rather than a solution
A suspension dosage form is superior to solution because of:
- ) Solubility
- ) Chemical stability
- ) Palatability
Know when a suspension is preferred to a tablet dosage form
A suspension has advantages over tablets because of:
- ) Flexibility of dose
- ) Ease of swallowing
- ) Dissolution rate
Based on Stokes Law, what factors affect the velocity of sedimentation of a suspension dosage form
x
List common methods of particle size reduction
Micropulverization e.g. impact mill 10 - 50 micron for oral and topical suspensions
Fluid energy grinding e.g. jet milling/micronizing < 10 microns for parenteral and opthalmic suspensions
Spray drying < 5 microns
What processes occur during aging of a suspension to bring delta G toward 0?
Aggregation and crystal growth…in emulsions this is called coalescence
Know inter particle forces important in suspension dosage forms.
Van de Waals attractive forces - attractive forces increase as particles get closer
Electrostatic repulsive forces - particles of the same charge, they tend to repell each other
Steric repulsive forces - hydrophilic colloids is an example of this steric repulsion
Hydration repulsive forces - water forms a layer around particle and helps repell each other.
Compare dispersion vs. flocculation.
Dispersion system all the particles are far apart. At certain distances they are repelling each other. But once they settle, they form a compact cake which cannot be reversed.
Flocculation groups of particles that settles fast but less prone to compaction and breaks up easily because they maintain a certain distance from each other.
Understand the basis of Newtonian and non-Newtonian flows
Water will flow proportionally to the amount of force you apply. Polymers show non-newtonian flow (kinda like ketchup. It doesn’t ready flow without some help, but once it starts its going.)
Know how shear-thinning rheology can be used to prepare suspensions.
This represents the strength of the attractive forces of the secondary minimum. Its thick in the undisturbed state, but thins as shear force is applied. Like ketchup.
Know the usual components of suspension dosage forms
API, vehicle, buffer, preservative, flocculating agent, structured vehicle system, wetting agent, antifoaming agent, flavor and sweetener
What is a polymer?
a large molecule made up of MANY small repeating units (PARTS). Chain of single molecules…monomer, dimer, oligomer, polymer…
Synthetic polymers vs. Natural polymers
Natural: Nucleic acids (DNA, RNA), proteins (gelatin) and polysaccharides (cellulose, chitosan, alginic acid)
Synthetic: most things that begin with poly-. Certain exceptions teflon, kevlar, nylon, silicon rubber, rayon
How to name a polymer
Its a repeating unit…so Poly(repeating unit)…polyacrylate is acrylate repeated many times. In most cases the repeating unit is in parenthesis but not always.
Two types of polymer synthesis
Addition polymerization:
Involves initiation, propagation and termination. Sometimes called free radical or chain polymerization. e.g. polyacrylate, polystyrene
Condensation polymerization: Two or more monomers carrying different reactive functional groups interact with each other. e.g. nylon
Know the difference between Mn and Mw
Mn = number average Mw = weight average
When talking about polymer, we usually use Mw
What does the polydispersity mean?
Mw/Mn = 1, then every polymer has the same molecular weight. However, if Mw/Mn is»_space; 1 (Mw»Mn) this is polydispersed, meaning a broad distribution of molecular weights
Fine particles are made up of solids and those solids can be hydrophobic or hydrophilic. When you drop water on the those surfaces and if you can measure the angle you can determine they hydrophobicity from the contact angle.
If the contact angle is > 90 degrees, the solid is hydrophobic. If the angle is
Which of the instability factors of emulsions is readily reversible and how is it done?
creaming / shake it up
A large negative value of V would indicate ______ and a large positive value of V would indicate ________.
floaters / sinkers
** know how the interfacial tension occurs and what is the function of the surfactants to change the interfacial tension
x
If you add a surfactant, the interfacial tension becomes _____ (higher or lower).
lower, because it serves as a piece maker at the interface
Understand the formation of micelles in solution of surfactants and their utility
x
How does each emulsifier work to stabilize the emulsion?
x
In an emulsion the dispersed part is _____ and in a suspension the dispersed part is _____.
liquid / solid
Suspensions follow first order kinetics which is linear because the solid particle are more stable than pure solution, which follows first order kinetics.
x
_______ is one reason we would select suspension over solution.
Another reason:
To _______ the solubility of water insoluble drugs.
Another reason:
A suspension will _____ the unfavorable taste of some solid dosage forms
Stability / increase / reduce
There are some drugs that are absolutely water insoluble (like brick dust). For those drugs we purposefully put them in suspension.
x
In suspension the solid particles are very very small which tremendously increases _______ ______.
surface area
List 3 advantages of suspensions over tablets.
- ) flexibility of dose
- ) Ease of swallowing
- ) Dissolution rate
Continuous in emulsion is synonymous with ____ in suspension.
vehicle
Requirements for ideal solution: (Desirable Properties slide)
- ) Should not be too thick or too thin
- ) It should not settle easily or flow easily
- ) Particles should not aggregate over time
If the particles in a suspension were to settle to quickly, how could you slow them down. List some methods.
- ) Decrease the size of the particle.
2. ) Change the vehicle
Examples of ways to stabilize a suspension i.e. slow the settling
x
3 types of suspension
Dispersed suspension
Flocculated suspension
Structured vehicle system
Bottom line for suspension….
it must be stable and easy to use
Goal of the dispersed suspension system is to…
reduce the settling as much as possible
How would you produce a dispersed system? (i.e. slow the settling) (Stokes Law)
reduce particle size
increase the viscosity
increase the density of the liquid vehicle
Flocculated system, you actually intentionally create….
bigger particles…actually temperary clusters of smaller particles…they will settle fast, but are very easy to resuspend
Structured vehicle system
all about the rheology you manipulate the way suspension liquid flow = stable particle suspension
Main difference between emulsion and suspension…
the dispersed phase of emulsion is liquid and the dispersed phase of the suspension is solid
The particles in a suspension are usually more dense than the liquid phase, so a disadvantage of a suspension is ______. How do we combat that? We try and reduce it.
settling
Repulsive and attractive forces are greatest when particles are (closer or farther) to/from one another?
closer
One of the characteristics used to describe a flocculated system is….
degree of flocculation
Rheology describes the flow characteristics.
x
Shear rate =
that rate at which liquid flows.
Examples of non-newtonian flow…
plastic, pseudo plastics, dilatant
Define pseudoplastic AKA shear-thinning
the fluids velocity decreases with an increasing rate of shear force. The more force you apply, the better the liquid flows
Define dilantant AKA shear-trickening
As you apply shear force, it becomes thicker.
Define newtonian flow
x
Define non newtonian flow
x
Define plastic flow
x
Flocculation vs. structured vehicle system
Both are ways to prepare a suspension.
Flocculated system: Manipulate the repulsive or attractive force between particles in a suspension so that they maintain distances with weak attractive forces. They are comfortable at certain distances but when you apply a certain force they can easily fall apart.
Structured vehicle system we manipulate the vehicle by adding clay particle or polymers so the vehicle will have non-newtonian flow properties…ie plastic or pseudoplastic. Its a gel like material, but when we shake it, it become more fluid.
Define thixotropy
The reversibility to go from a thick undisturbed state to a thin, flowing state with shear force is applied.
One of the reasons we like to make suspension is to improve the bioavailability of hydrophobic drugs. Suspension allows you to have a large surface area. Hydrophobic drugs have a larger contact angle and and therefore larger surface area.
x
A surface active agent added to reduce the surface tension between vehicle (usually water) and the particles = known as a wetting agent. e.g. polysorbate 80 (tween 80)
x
List one way to get rid of air pockets at the surface.
introduce a wetting agent
Label each as Natural or Synthetic polymers:
- ) Cellulose
- ) Kevlar
- ) DNA
- ) RNA
- ) Rayon
- ) Gelatin
- ) Chitosan
- ) Silicon Rubber
- ) Alginic acid
- ) Nylon
- ) Teflon
- ) Polysaccharide
- ) Nat
- ) Syn
- ) Nat
- ) Nat
- ) Syn
- ) Nat
- ) Nat
- ) Syn
- ) Nat
- ) Syn
- ) Syn
- ) Nat
