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PHYPHARM > COARSE DISPERSION > Flashcards

COARSE DISPERSION Flashcards

1
Q
  • Particle size between greater than 500 nm
  • Visible under ordinary microscope
  • Do not pass through filter paper
  • Do not pass through semipermeable membrane
  • Do not diffuse
A

COARSE DISPERSION

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2
Q

Most pharmaceutical suspensions and emulsions are

A

coarse dispersions

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3
Q

SUSPENSION

Insoluble Solid, internal

A

dispersed phase

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4
Q

SUSPENSION

liquid, external

A

dispersion medium

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5
Q

SUSPENSION

concentration of externally applied suspensions

A

.>20%

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6
Q

SUSPENSION

concentration of Parenteral suspensions

A

0.5 - 30%

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7
Q

Advantages of Pharmaceutical Suspension

Make insoluble drugs more ____

A

palatable

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8
Q

Advantages of Pharmaceutical Suspension

Provide suitable dosage form for ____ to skin and mucous membrane while retaining the grittiness of the solid particle

A

dermatologic materials

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9
Q

Advantages of Pharmaceutical Suspension

Parenteral administration of ____ drugs

A

water-insoluble

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10
Q

Characteristics of an Acceptable Suspension

Suspended material should NOT ____

A

settle rapidly

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11
Q

Characteristics of an Acceptable Suspension

Sediments do NOT for a ____

A

hard cake

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12
Q

Characteristics of an Acceptable Suspension

____ when shaken

A

readily dispersed

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13
Q

Characteristics of an Acceptable Suspension

Not too ____

A

viscous

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14
Q

Characteristics of an Acceptable Suspension

for lotions:
Easily ____

A

spread

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15
Q

Characteristics of an Acceptable Suspension

for lotions:
____ quickly

A

dry

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16
Q

Characteristics of an Acceptable Suspension

for lotions:
have acceptable ____ and ____

A

color & odor

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17
Q

Physical Stability of Suspensions

Particles do not ____

A

aggregate

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18
Q

Physical Stability of Suspensions

They remain ____ throughout.

A

uniformly distributed

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19
Q

Physical Stability of Suspensions

Easily resuspended by ____

A

moderate agitation

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20
Q

light fluffy conglomerates held by weak van der Waals forces

A

flocs / floccules

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21
Q

Properties of Suspended Particles

Tend to ____

A

flocculate

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22
Q

flocs or floccules are held by

A

weak van der waals forces

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23
Q
  • particles adhere by stronger forces
  • leads to CAKING
A

aggregates

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24
Q

growth and fusing of aggregates

A

caking

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25
Q

FLOCCU OR DEFLOCCU

Sediments are loosely packed
(FLOCS)

A

FLOCCULATED

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26
Q

FLOCCU OR DEFLOCCU

Sediment is closely packed (AGGREGATES) and forms a hard cake

A

DEFLOCCU

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27
Q

FLOCCU OR DEFLOCCU

Sediment rapidly forms

A

FLOCCU

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28
Q

FLOCCU or DEFLOCCU

Sediments slowly forms

A

DEFLOCCU

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29
Q

FLOCCU or DEFLOCCU

High sedimentation rate
(settles rapidly)

A

FLOCCU

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30
Q

FLOCCU or DEFLOCCU

Low sedimentation rate
(settles slowly)

A

DEFLOCCU

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31
Q

FLOCCU or DEFLOCCU

Easily redispersed when shaken

A

FLOCCU

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32
Q

FLOCCU or DEFLOCCU

Difficult to redisperse

A

DEFLOCCU

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33
Q

FLOCCU or DEFLOCCU

Pharmaceutically Elegant

34
Q

Velocity of sedimentation is expressed by

A

STOKE’S LAW

35
Q

Dilute Suspension

A

FREE SETTLING

36
Q

.>5% Suspension

A

HINDERED SETTLING

37
Q

settle more rapidly

A

LARGER PARTICLES

38
Q

Settling in flocculated systems

A

SUBSIDENCE

39
Q

FORMULA

sedimentation volume of flocculated

A

F = Vu / Vo

Vu - final volume
Vo - original volume

40
Q

FORMULA

sedimentation volume of deflocculated

A

F∞ = Vu / Vo

41
Q
  • determines the acceptability of a solution
  • more fundamental parameter
A

degree of flocculation

42
Q

FORMULA

degree of flocculation

A

β = F / F∞

F - sedimentation volume flocculated
F∞ - sedimentation volume defloccul

43
Q

pharmaceutically acceptable

44
Q

Components of Suspension

surfactants that decrease the solid–liquid interfacial tension and contact angle between the solid particles and the liquid vehicle.

A

wetting agents

45
Q

Components of Suspension

  • Neutral electrolytes that are capable of reducing the zeta potential of suspended charged particles to zero
  • increase sedimentation volume
  • to electrify
A

flocculating agents

46
Q

Components of Suspension

do not appreciably lower the surface and interfacial tension but are used to produce deflocculated suspensions

A

dispersing agents (deflocculants)

47
Q

Components of Suspension

retard settling and agglomeration of the particles by functioning as an energy barrier, which minimizes interparticle attraction

A

suspending agents

48
Q

SUSPENDING AGENTS

  • Do not reduce interfacial tension
  • Used in low concentration (0.1%)
  • Forms mechanical barrier around particles
A

protective colloids

49
Q

Preparation of Suspensions

applicable to only those drugs where solubility depends on the pH value.

A

pH precipitation

50
Q

Preparation of Suspensions

the vehicle must be formulated so that the solid phase is easily wetted and dispersed

A

dispersion method

51
Q

Preparation of Suspensions

Wetting agent + Vehicle → + Drug → Slurry → Sieved → Agitated → + Flocculating agent → Agitated → Allowed to settle → + Adjuvants → Dilute to final volume

A

CONTROLLED FLOCCULATION

52
Q

A thermodynamically unstable system consisting of at least two immiscible liquids

53
Q

Pharmaceutical Emulsions

Dispersed phase (liquid) as

54
Q

Pharmaceutical Emulsions

Dispersion medium as

A

other liquid

55
Q

pharmaceutical emulsions are stabilized by

A

emulsifying agent

56
Q

THEORIES OF EMULSIFICATION

the interfacial tension between two immiscible liquids is reduced by surfactants

A

surface tension theory

57
Q

THEORIES OF EMULSIFICATION

if nonpolar end of the emulsifying agent is smaller, the emulsion is O/W

A

oriented wedge theory

58
Q

THEORIES OF EMULSIFICATION

emulsifying agent forms a film over one phase resulting to globules

A

interfacial film theory

59
Q
  • surfactants reduce interfacial tension by adsorption at the O/W interface to form monomolecular film (reduces coalescence)
  • reduction of the surface free energy and the tendency to coalescence
  • combination of emulsifiers rather than single agents are frequently used
A

MONOMOLECULAR ADSORPTION

60
Q

emulsion is a function of the relative solubility of the surfactant

A

BANCROFT’S RULE

61
Q
  • finely divided wetted solids by oil & water can act as emulsifying agents
  • they form a film a particulate film around the droplet to prevent coalescence
A

Solid-particle adsorption

62
Q

Dispersed Phase → Oil
Continuous Phase → Water
* usually for oral administration
* emulsifiers: SLS, triethanolamine

A

oil in water O/W emulsion

63
Q

Dispersed Phase → Water
Continuous Phase → Oil
* usually for external application
* emulsifiers: sodium palmitate, sorbitan esters (Spans)

A

water in oil W/O emulsion

64
Q
  • complex polydisperse systems
  • both W/O & O/W exist simultaneously and are stabilized by lipophilic and hydrophilic surfactants
  • used for controlled, sustained, or targeted delivery, enzyme immobilization, taste masking, and other applications

w/o/w, o/w/o

A

MULTIPLE EMULSION

65
Q
  • a system of water, oil, and amphiphile, which is a single optically isotropic and thermodynamically stable liquid solution
  • almost appear transparent or clear
A

microemulsions

66
Q

microemulsions are also known as

A

micellar emulsions

67
Q
  • kinetically stable liquid-in-liquid dispersions with droplet sizes on the order of 100nm
  • their small size leads to useful properties such as high surface area per unit volume, robust stability, optically transparent appearance, and tunable rheology
A

nanoemulsions

68
Q

Method of determining the type of emulsion

a small quantity of water-soluble dye such as methylene blue or amaranth may be mixed with the emulsion

69
Q

Method of determining the type of emulsion

involves diluting the emulsion with either water or oil

A

dilution test

70
Q

Method of determining the type of emulsion

uses a pair of electrodes connected to an external eletcric source and immersed in the emulsion

A

conductivity test

71
Q

Advantages of Pharmaceutical Emulsions

a convenient means of orally-administering water-insoluble liquids.
(e.g. fat-soluble vitamins)

A

O/W emulsions

72
Q

Advantages of Pharmaceutical Emulsions

spread easily, water-washable, less-greasy and non-staining

A

creams & lotions

73
Q

random movement of particles suspended in fluids

74
Q

The process where the particles adhere by stronger forces in compacted cake (worse than flocculation).

A

aggregation

75
Q

Growth and fusing together of crystals in the precipitate to produce a solid aggregate

76
Q
  • Counteracts sedimentation of particles with a diameter of about 2 to 5 micrometers
  • The dispersed material is kept in random motion.
  • It is not present in pharmaceutical suspensions that has suspending agents – is eliminated when the sample has 50% glycerin (5 centipoise)
  • Only happens in** diluted suspensions**
A

brownian movement

77
Q
  • Known as shear-thinning systems
  • Viscosity of a pseudoplastic substance decreases with increasing rate of shear.
  • Shaking or agitation decreases viscosity
A

pseudoplastic flow

78
Q
  • Known as Bingham bodies
  • Does not begin to flow until shearing stress corresponding to the yield value is exceeded
  • Applicable to semisolids
  • It will only start to flow after reaching the yield value
A

plastic flow

79
Q
  • An isothermal and comparative slow recovery, on standing of a material, of a consistency lost through shearing.
  • Gradually becomes viscous if there is no agitation
A

Thixotropy

80
Q

Characterized by the absence of coalescence of the internal phase, absence of creaming, and maintenance of elegance with respect to appearance, color, odor, and other physical properties

A

stable emulsion

81
Q

An agglomeration of the internal phase and its separation from the product.

A

unstable emulsion

82
Q

Results from flocculation and concentration of globules of the internal phase but does not necessarily lead to instability however,
o It represents potential steps towards complete coalescence of the internal phase.
o May result in a lack of uniformity of drug distribution and unless thoroughly shaken before administration leads to variable dosage.
o Affects the visual appeal of an emulsion

PHYPHARM (28 decks)

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