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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
Q

What is interfacial tension?

A

The force of attraction between molecules at the interface of two fluids

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26
Q

What is surface tension?

A

The force of attraction between molecules at the interface of a fluid and air

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27
Q

Why is high interfacial tension bad?

A

imbalance leads to movement of molecules from the interface into the bulk phase; fewer molecules per unit area at the interface.

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28
Q

Does strong intermolecular forces in the bulk phase result in high or low interfacial tension?

A

High

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29
Q

What does a great tendency between phases to interact indicate?

A

Low interfacial tension

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30
Q

How does raising the temperature affect interfacial tension?

A

Lowers the interfacial tension

31
Q

What is an emulsifying agent?

A

added to stabilize an emulsion; usually a surfactant, polymer (hydrophilic colloid), or a fine solid particle film.

32
Q

What is the purpose of a surfactant?

A

Amphiphilic; reduces interfacial tension

33
Q

What is the critical micelle concentration?

A

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
Q

How can surfactants be classified?

A

Anionic, cationic, zwitterionic, and nonionic

35
Q

What is the hydrophile- lipophile balance? (HLB)

A

A measure of the relative contributions of the hydrophilic and lipophilic regions of a surfactant.

36
Q

What does a low HLB indicate?

A

Greater lipid solubility

37
Q

What is the rule of Bancroft?

A

The phase in which a surfactant is more soluble becomes the continuous phase

38
Q

What are hydrophilic colloids?

A

a hydrophilic polymer used to form oil in water emulsions

39
Q

Do hydrophilic colloids (polymers) lower the interfacial tension?

A

no; just increase the viscosity of water

40
Q

What is the role of finely divided solid particles in an emulsion?

A

emulsifying agent; forms a film of fine particles at the interface of two liquids

41
Q

What does an HLB <10 indicate?

A

Water in oil emulsion (more lipophilic)

42
Q

What does an HLB >10 indicate?

A

an oil in water emulsion (more hydrophilic)

43
Q

What is creaming?

A

formation of sediment (separation of two liquid phases)

44
Q

IS creaming reversible?

A

Yes, IF the interfacial film maintains the integrity of individual droplets

45
Q

What is coalescence?

A

Increase in droplet size because the interfacial film cannot maintain the integrity of individual droplets.

46
Q

Is coalescence reversible?

A

No, leads to oil layer and water layer; broken emulsion

47
Q

What is phase inversion?

A

O/W emulsion converted to W/O

48
Q

What are suspensions?

A

Liquid preparations consisting of solid particles dispersed throughout a liquid phase in which the particles are not soluble.

49
Q

What are the benefits of suspensions over solutions?

A

used when active ingredient not soluble; very chemically stable; masks taste of AI

50
Q

What are the benefits of suspensions over tablets?

A

flexible dosing; easy to swallow; faster dissolution in the body

51
Q

What are desirable properties of suspensions?

A

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
Q

What techniques are used to obtain small particle size for suspensions?

A

micro pulverization, fluid energy grinding, spray drying

53
Q

What technique obtains the smallest particle size for emulsion?

A

Spray drying

54
Q

How do suspensions become more thermodynamically stable over time?

A

Reducing surface area; aggregation, crystal growth

55
Q

as distance between particles increases, what happens to the interparticle forces?

A

attractive and/or repulsive forces increase

56
Q

What is a dispersed suspension?

A

Repulsive forces are dominant; particles settle very slowly; once particles are settled, it is difficult to resuspend

57
Q

What is controlled flocculation?

A

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
Q

What is a structured vehicle?

A

Thickens the dispersion medium and helps to suspend particles

59
Q

What is newtonian flow?

A

viscosity is constant

60
Q

What is non-newtonian flow?

A

plastic, pseudoplastic, dilatant

61
Q

What type of suspensions have plastic flow?

A

flocculated suspensions; has a minimum force required for fluid to flow

62
Q

What type of suspensions have pseudoplastic flow?

A

Polymer suspensions; no flow at low force, does flow at high force

63
Q

What type of suspension has dilatent flow?

A

suspensions with high solids content; think cornstarch and water

64
Q

What is thixotrophy?

A

The ability of a system that was disturbed by an applied shear stress to return to it’s undisturbed structure

65
Q

What types of suspensions show thixotrophy?

A

Plastic and pseudoplastic

66
Q

What does a contact angle of less than 90 degrees indicate about a solid?

A

It is hydrophilic; low interfacial tension

67
Q

What does a contact angle of greater than 90 degrees indicate about a solid?

A

It is hydrophobic; large interfacial tension

68
Q

What does a wetting agent do?

A

Reduce surface tension of an aqueous vehicle

69
Q

What are examples of natural polymers?

A

nucleic acids (DNA, RNA), proteins (gelatin), polysaccharides (cellulose, chitosan, alginic acid)

70
Q

What are examples of synthetic polymers?

A

Polyethylene, teflon, kevlar, nylon, rayon

71
Q

What is condensation polymerization

A

Two different monomers with different functional groups interact with one another

72
Q

What is another name for condensation polymerization?

A

Step polymerization

73
Q

What does addition polymerization consist of?

A

Initiation, propagation, and termination

74
Q

What are other names for addition polymerization?

A

Free-radical polymerization; chain polymerization

Dosage II (4 decks)

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