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Dosage II > Exam 1 > Flashcards

Exam 1 Flashcards

1
Q

What is the difference between a solution, emulsion, and suspension?

A

Solution: homogenous molecular dispersion
Emulsion: oil suspended in water or water suspended in oil
Suspension: solid suspended in water or oil

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2
Q

Advantages of solution dosage forms

A

Homogenous, easy to manufacture, and good bioavailability

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3
Q

Disadvantages of solution dosage forms

A

Less stable than solid dosage forms/ suspensions

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4
Q

Henderson Hasselbach equation

A

pH = pKa + log[A-]/[HA]

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5
Q

pH –> [H30+]

A

[H30+] = 10^-pH

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6
Q

What is the variable C in the Van Slyke equation?

A

C= total buffer concentration = [HA] + [A-]

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7
Q

When is buffering capacity at its max?

A

When pH=pKa

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8
Q

how do you convert from pKa to Ka?

A

pKa = -log(Ka)

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9
Q

Should you choose a pH at a high or low k value?

A

Low K value

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10
Q

What is the purpose of an anti-microbial preservative?

A

Protect patients from pathogens; maintain potency and stability of dosage forms

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11
Q

What is an ideal preservative?

A

Effective in low concentrations against a wide variety of organisms; soluble in formation, non-toxic, stable

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12
Q

What is a problem with parabens as preservatives?

A

low solubility; skin sensitization in dermatological products

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13
Q

What is a problem with weak acids as preservatives?

A

only the unionized species are effective as preservatives

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14
Q

What is the main degradation pathway of pharmaceuticals?

A

oxidation

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15
Q

What is auto-oxidation?

A

an automatic reaction with oxygen without a drastic external interference

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16
Q

What is oxidation initiated by?

A

heat, light, peroxides, metals (free radicals)

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17
Q

What is an antioxidant?

A

a compound that inhibits oxidation

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18
Q

What is a free radical scavenger?

A

An antioxidant that delays oxidation by rapidly reacting with free radicals.

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19
Q

What is a reducing agent?

A

Removes O2 from the system by being more readily oxidized

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20
Q

What is a chelating agent?

A

Removes metals that catalyze oxidation reactions

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21
Q

What is an emulsion?

A

a system of two liquids (water and oil), where one is dispersed as droplets

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22
Q

What “phases” does an emulsion consist of?

A

a dispersed phase and a continuous phase

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23
Q

What is an oil in water emulsion used for orally?

A

mask the taste of an oil; enhance absorption of an oil (increase bioavailability)

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24
Q

what is intravenous lipid emulsion and what is it used for?

A

oil in water emulsion; used for parenteral nutrition

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25
What is interfacial tension?
The force of attraction between molecules at the interface of two fluids
26
What is surface tension?
The force of attraction between molecules at the interface of a fluid and air
27
Why is high interfacial tension bad?
imbalance leads to movement of molecules from the interface into the bulk phase; fewer molecules per unit area at the interface.
28
Does strong intermolecular forces in the bulk phase result in high or low interfacial tension?
High
29
What does a great tendency between phases to interact indicate?
Low interfacial tension
30
How does raising the temperature affect interfacial tension?
Lowers the interfacial tension
31
What is an emulsifying agent?
added to stabilize an emulsion; usually a surfactant, polymer (hydrophilic colloid), or a fine solid particle film.
32
What is the purpose of a surfactant?
Amphiphilic; reduces interfacial tension
33
What is the critical micelle concentration?
At a certain concentration of surfactant, surface tension cannot be reduced any more; surface tension is constant at and after the CMC (critical micelle concentration)
34
How can surfactants be classified?
Anionic, cationic, zwitterionic, and nonionic
35
What is the hydrophile- lipophile balance? (HLB)
A measure of the relative contributions of the hydrophilic and lipophilic regions of a surfactant.
36
What does a low HLB indicate?
Greater lipid solubility
37
What is the rule of Bancroft?
The phase in which a surfactant is more soluble becomes the continuous phase
38
What are hydrophilic colloids?
a hydrophilic polymer used to form oil in water emulsions
39
Do hydrophilic colloids (polymers) lower the interfacial tension?
no; just increase the viscosity of water
40
What is the role of finely divided solid particles in an emulsion?
emulsifying agent; forms a film of fine particles at the interface of two liquids
41
What does an HLB <10 indicate?
Water in oil emulsion (more lipophilic)
42
What does an HLB >10 indicate?
an oil in water emulsion (more hydrophilic)
43
What is creaming?
formation of sediment (separation of two liquid phases)
44
IS creaming reversible?
Yes, IF the interfacial film maintains the integrity of individual droplets
45
What is coalescence?
Increase in droplet size because the interfacial film cannot maintain the integrity of individual droplets.
46
Is coalescence reversible?
No, leads to oil layer and water layer; broken emulsion
47
What is phase inversion?
O/W emulsion converted to W/O
48
What are suspensions?
Liquid preparations consisting of solid particles dispersed throughout a liquid phase in which the particles are not soluble.
49
What are the benefits of suspensions over solutions?
used when active ingredient not soluble; very chemically stable; masks taste of AI
50
What are the benefits of suspensions over tablets?
flexible dosing; easy to swallow; faster dissolution in the body
51
What are desirable properties of suspensions?
should not settle rapidly, should not form a hard cake when settled; should be easy to administer (not too viscous); particle size should remain constant
52
What techniques are used to obtain small particle size for suspensions?
micro pulverization, fluid energy grinding, spray drying
53
What technique obtains the smallest particle size for emulsion?
Spray drying
54
How do suspensions become more thermodynamically stable over time?
Reducing surface area; aggregation, crystal growth
55
as distance between particles increases, what happens to the interparticle forces?
attractive and/or repulsive forces increase
56
What is a dispersed suspension?
Repulsive forces are dominant; particles settle very slowly; once particles are settled, it is difficult to resuspend
57
What is controlled flocculation?
Repulsive and attractive forces are in balance; particles are weakly attracted and form aggregates known as floccules; sediment settles quickly and has high volume; easy to redisperse
58
What is a structured vehicle?
Thickens the dispersion medium and helps to suspend particles
59
What is newtonian flow?
viscosity is constant
60
What is non-newtonian flow?
plastic, pseudoplastic, dilatant
61
What type of suspensions have plastic flow?
flocculated suspensions; has a minimum force required for fluid to flow
62
What type of suspensions have pseudoplastic flow?
Polymer suspensions; no flow at low force, does flow at high force
63
What type of suspension has dilatent flow?
suspensions with high solids content; think cornstarch and water
64
What is thixotrophy?
The ability of a system that was disturbed by an applied shear stress to return to it's undisturbed structure
65
What types of suspensions show thixotrophy?
Plastic and pseudoplastic
66
What does a contact angle of less than 90 degrees indicate about a solid?
It is hydrophilic; low interfacial tension
67
What does a contact angle of greater than 90 degrees indicate about a solid?
It is hydrophobic; large interfacial tension
68
What does a wetting agent do?
Reduce surface tension of an aqueous vehicle
69
What are examples of natural polymers?
nucleic acids (DNA, RNA), proteins (gelatin), polysaccharides (cellulose, chitosan, alginic acid)
70
What are examples of synthetic polymers?
Polyethylene, teflon, kevlar, nylon, rayon
71
What is condensation polymerization
Two different monomers with different functional groups interact with one another
72
What is another name for condensation polymerization?
Step polymerization
73
What does addition polymerization consist of?
Initiation, propagation, and termination
74
What are other names for addition polymerization?
Free-radical polymerization; chain polymerization

Dosage II (4 decks)

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