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Pharmaceutical Sciences > PSII Exam II > Flashcards

PSII Exam II Flashcards

1
Q

Define a dispersed system

A

A mixture of one phase in another largely immiscible phase.

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2
Q

Define a suspension

A

Solid particles dispersed in a liquid medium.

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3
Q

Define an emulsion

A

Liquid droplets dispersed in a liquid medium.

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4
Q

Define a molecular dispersion

A

A true solution; particle size less than 1 nanometer.

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5
Q

Define a colloidal dispersion

A

Particle size less than half a micron.

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6
Q

Define a coarse dispersion

A

Particle size greater than half a micron.

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7
Q

What are three important stability characteristics of PHARMACEUTICAL dispersed systems?

A
  1. Uniform distribution
  2. Aggregation rate controlled.
  3. Flocculation controlled.
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8
Q

What are three fundamental physical chemistry concepts for PHARMACEUTICAL dispersed systems?

A
  1. Interfacial properties
  2. Vehicle viscosity
  3. Dispersed particle properties
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9
Q

What are two (2) mechanisms to impart stability common to pharmaceutical dispersed systems?

A
  1. Repulsion of particles due to surface charge (zeta potential) [Electrical Barrier]
  2. Physical hindrance by surfactant. [Mechanical Barrier]
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10
Q

What are three (3) de-stabilization mechanisms for a pharmaceutical dispersed system?

A
  1. Temperature changes (solubility, freezing)
  2. Microbial growth (degredation)
  3. Addition of chemical agents (pH-solubility, ionic strength).
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11
Q

What are two ways to assess a suspension?

A
  1. SEDIMENTATION VOLUME, F (ratio of final sedimentation height and original height -> magnitude increases as sediment height increases [due to greater # of settled particles].
  2. DEGREE OF FLOCCULATION, Beta (ratio of flocculated height to unflocculated height -> magnitude increases as sediment height increases [due to greater space between particles].
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12
Q

According to Stokes Law, what are two methods for decreasing the rate of settling (velocity of creaming)?

A
  1. Decrease mean particle diameter. At
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13
Q

What are two methods for increasing the degree of flocculation?

A
  1. Electrolyte interaction with shear plane (affecting zeta potential).
  2. Mechanical barrier with polymer or surfactant. (Requires optimal concentration for ‘bridging’)
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14
Q

What are three (3) useful characteristics of surfactants?

A
  1. Decrease interfacial tension
  2. Promote wetting of solids
  3. Facilitate dispersion
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15
Q

Define a Newtonian liquid

A

Viscosity stays constant. Therefore, rate of shear increases proportionally to shear stress.

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16
Q

What are three (3) classes of Non-Newtonian rheology?

A
  1. Plastic flow
  2. Pseudoplastic flow
  3. Dilatant Flow
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17
Q

Define plastic flow behavior

A
  1. Below yield value, system exhibits elastic behavior.

2. Above yield value, system exhibits Newtonian behavior.

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18
Q

Define pseudoplastic flow behavior

A

Viscosity decreases with increase in shear stress – shear-thinning behavior.

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19
Q

Define dilatant flow behavior

A
  1. Viscosity increases with increase in shear stress – shear-thickening behavior.
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20
Q

Define thixotropy

A

Thixotropy is related to the time-dependent restoration of structure following shear stress for shear-thinning systems.

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21
Q

How is thixotropy useful in pharmaceutical formulations?

A

Example: Shaking a nasal spray before use allows delivery into nasal cavity; viscosity recovery prolongs residence.

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22
Q

What kinds of mechanical barriers can emulsifying agents form?

A
  1. Monomolecular films
  2. Polymolecular films
  3. Adsorbed solid particles
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23
Q

What is a necessary chemical property for an emulsifying agent to be effective?

A

It must have an affinity for both phases so that it is active at the interface.

24
Q

Describe the hydrophilic-lipothilic balance (HLB)

A

Scale of 1-60 that defines relative affinity for water and oil.

25
Q

What is the HLB value of a lipophilic emulsifying agent?

A

1-10

26
Q

What is the HLB value of a hydrophilic emulsifying agent?

A

> 10

27
Q

What is Bancroft’s Rule?

A

The phase in which an emulsifying agent has the greater affinity constitutes the continuous phase.

28
Q

Discuss two (2) important considerations when combining emulsifying agents.

A
  1. The ‘effective’ HLB is a weighted average of agents.

2. Structural characteristics (e.g. double bond) may result in incompatibility.

29
Q

Define a pharmaceutical gel

A

Semisolid system consisting of a condensed mass (matrix) enclosing a liquid.

30
Q

Define a jelly

A

A gel in which the matrix contains a high water content.

31
Q

Give two (2) examples of a single phase gel

A
  1. Carbomer

2. Hypromellose

32
Q

What is a hydrogel?

A

Liquid phase is water – gel network is inorganic or organic

33
Q

Give three (3) examples of organic hydrogels

A
  1. Carbomer
  2. Poloxamer
  3. Sodium carboxymethylcellulose
34
Q

What are four (4) types of structures seen in a gel matrix?

A
  1. Random coils
  2. Helix
  3. Stacks
  4. ‘House of Cards’
35
Q

What are four (4) factors related to gel formation?

A
  1. Gelling agent concentration
  2. Solution pH
  3. Ion cross-linkage
  4. Thermal gelation
36
Q

Give an example of a gel formed with ion cross-linkage

A

Calcium alginate gels are formed with Ca2+ and Sodium Alginate.

37
Q

Give an example of a gel formed with solution pH

A

Carbopol gels are ionized (pKa 5-6) and electrostatic repulsion results in a gel network forming.

38
Q

Give an example of a gel formed with thermal gelation

A

Poloxamer is dehydrated at increased temperatures to form micelles which aggregate to form a gel network.

39
Q

What is a special consideration when using hydrogels of cellulose derivatives?

A

Levigation is required to help wet the clumped polymer when added to water..

40
Q

What is a special consideration when using sodium carboxymethylcellulose?

A

Optimal viscosity for NaCMC is observed at pH 7-9.

41
Q

Define an ointment

A

Semisolid preparation intended for external use. API is dissolved, suspended or emulsified.

42
Q

What are the four (4) USP classifications of ointment bases?

A
  1. Hydrocarbon (oleaginous) – oily with limited aqueous.
  2. Absorption – oily with enhanced aqueous.
  3. Water removable – oil in water emulsions.
  4. Water soluble – only water components.
43
Q

Define a cream

A

A semisolid emulsion.

44
Q

Define a paste

A

A semisolid with a large solid concentration.

45
Q

Give two (2) examples of oleaginous bases

A
  1. 95% petrolatum + 5% wax

2. Liquid petrolatum with low density polyethylene resin.

46
Q

Give three (3) examples of an absorption base

A
  1. Aquaphor – a commercially refined hydrophilic petrolatum.
  2. Nivea Cream
  3. Eucerin
47
Q

Give three (3) examples of water-washable bases

A
  1. Dermabase
  2. Cetaphil
  3. Aquaphilic
48
Q

Give an example of a water-soluble base

A

Polybase

49
Q

What are four (4) characteristics of ointment bases?

A
  1. Composition
  2. Occlusiveness
  3. Incorporation of API
  4. Feel and Washability
50
Q

Characterize hydrocarbon (oleaginous) bases (4 components)

A
  1. Composed of oily compounds
  2. Occlusive
  3. Incorporates hydrophobic API
  4. Greasy, non-washable
51
Q

Characterize absorption (anhydrous) bases (4 components)

A
  1. Composed of oily base + w/o emulsifier
  2. Occlusive
  3. Incorporates hydrophobic and small amounts of hydrophilic
  4. Greasy, non-washable
52
Q

Characterize water-washable bases (4 components)

A
  1. Composed of oil + water + o/w surfactant
  2. Non-occlusive
  3. Solids and small amount of aqueous solution – poor hydrophobic.
  4. Non-greasy and washable.
53
Q

Characterize water-soluble bases (4 components)

A
  1. Water soluble ingredients
  2. Non-occlusive
  3. Solids and aqueous solutions
  4. Non-greasy and washable.
54
Q

What are two (2) methods of preparing suppositories?

A
  1. Hand-rolling

2. Fusion molding

55
Q

Why are dosage calculations required for preparing drug-filled suppositories with fusion molding?

A

Components are measured by weight but dosage unit (suppository mold) is created by volume.

56
Q

Define Density Displacement Factor (DDF)

A

The weight of a drug in gram required to displace 1 g of base.

57
Q

What three (3) pieces of information are necessary to calculate a DDF?

A
  1. Weight of blank suppository.
  2. Weight of medicated suppository.
  3. Weight of drug per suppository.

Pharmaceutical Sciences (9 decks)

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