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Pharmacy > Performulation > Flashcards

Performulation Flashcards

1
Q

Factors affecting solubility

A
  • temp
  • pressure
  • molecular structure of solute
  • solvent characteristics
  • crystal characteristic
  • pH
  • common ion effect
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2
Q

How is solubility affected in endothermic reaction

A

Temp increases so solubility increases (kinetic energy increase with temp)

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3
Q

What happens when pH increases with weak acids

A

Ionisation increases

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4
Q

What happens when pH increases with weak bases

A

Ionisation decreases

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5
Q

How soluble is Amorphous ?

A

Very soluble

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6
Q

How to assess solubility ?

A

XS solute in solvent to dissolve
Removed undissolved solid
Molecules with e- absorb light
Amount of light absorbed proportional to analytical conc.

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7
Q

What is surface tension depended on?

A

Temperature

Impurities (surfactants)

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8
Q

What to use to measure surface tension?

A

Wilhelmy plate

Du Noüy ring (interfacial tension too)

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9
Q

How does wetting happen?

A

Result of intermolecular interactions at the S-L interface

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10
Q

Surfactant ceutical uses?

A
  • detergent
  • emulsifying agent
  • wetting agents
  • foaming agent
  • flocculating agent
  • solubilising agent
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11
Q

What happens when the surfactant concentration too much?

A

No more surface for surfactant molecules to line thus form micelles

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12
Q

Critical micelle concentration

A

Surfactant conc. above micelles form

  • in water, CMC decreases with increases molecular size of surfactant
  • bulkier surfactant =less molecules fit in give SA so lower CMC
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13
Q

What administration can emulsions be given in?

A

Oral
Parenteral
Topical

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14
Q

Single emulsion

A

Liquid droplets (disperse phase) in another liquid (continuous phase)

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15
Q

Double emulsion

A

Primary emulsion droplets in another liquid

EG: O/W/O Emulsion

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16
Q

Most emulsifiers are?

A

Surfactants and therefore amphipilic

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17
Q

What to emulsifiers mediate?

A

Molecular interactions at the interface between disperse and continuous phase

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18
Q

Stable emulsions called?

A

Meta stable

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19
Q

Different types on emulsion instability?

A

Flocculation
Creaming
Sedimentation
Cracking

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20
Q

Flocculation

A

Electrical double layer around particles

Flocs May fuse = coalescence

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21
Q

How can floc interactions be altered

A

With additives

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22
Q

Sedimentation and creaming

A

Patrick’s sink in continuous phase under opposing forces

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23
Q

Sedimentation rate increases with?

A
  • larger droplet size
  • lowkey fluid viscosity
  • greater density differences between droplet and continuous phase
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24
Q

If emulsifier is more soluble in water, what type of emulsion?

A

O/W emulsion

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25
Q

If emulsifier more soluble in oil, what type of emulsion?

A

W/O emulsion formed

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26
Q

What is crystalline structure?

A

Thermodynamically stable, sharp MPT

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27
Q

Polymorphism of same substance can differ in terms of:

A 
MPT
Density
Chemical reactivity 
Mechanical properties 
Dissolution rate
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28
Q

Polymorphs absorption

A

Is different and bioavailability despite identical formulation

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29
Q

What undergoes glass transition?

A

Amphorous

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30
Q

Compaction cycle

A

1-filling in die cavity
2-compression -die volume decreases
3-ejection - tablet pushed (lubrication)

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31
Q

Compression results in:

A

Reduced porosity
Reduced bulk volume
Increases bulk density

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32
Q

Mechanical properties required for compaction

A

Plasticity - deformed particles when compressed = greater cohesion
Brittleness - particles fragment = increase SA and surface energy = greater cohesion

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33
Q

What is tensile strength

A

Stress needed to fracture tablet. Reflects strength of inter-particle bonding

34
Q

If compaction pressure increases ?

A

Tensile strength increases

35
Q

If tablets are flat it convex ?

A

Lower tensile strength

36
Q

If the polymorph is stable?

A

Lower tensile strength

37
Q

Driving forces

A

Gravitational force, mechanical agitation

38
Q

Retardant forces

A

Cohesion /adhesion, friction, mechanical interlocking

39
Q

What does adhesion attract

A

2 chemically different surfaces

40
Q

What does cohesion attract?

A

Attractive forces between 2 chemically similar surfaces

41
Q

Example of adhesion/cohesion forces?

A
  • VDW
  • electrostatic attraction
  • capillarity forces (liquid bridges)
42
Q

How do VDW forces increase?

A

With particle size and proximity

Dominant effect on fine particles over gravity

43
Q

What do capillary forces do?

A

Adsorb moisture on particle surface, forming liquid bridges

44
Q

What are the factors affecting particle size? (To favour flow)

A 
Large particle size
Spherical particle 
SA of particle = small
High density
Looser packing geometry
Moderate moisture content
45
Q

What happens when there too much moisture with particles?

A

They clump together

46
Q

What is the angle of repose and how does it come about?

A

Cohesive powders flow less well and also pile up higher

=steeper slope, larger angle of repose = lower flowability

47
Q

Product quality aims from mixing?

A

Uniformity of mass
Reproducibility
Therapeutic efficacy
Patient safety

48
Q

What is a positive mixture ?

A

Approaches perfect mixture (eg: alcohol and water)

49
Q

What is a negative mixture?

A

Energy input required to mix components and maintain mixture
(Eg:emulsion)

50
Q

Neutral mixture ?

A

Energy input required to mix/segregate eg:powders/pastes

51
Q

Random mixture?

A

Group of particles adjacent to one another

Free flowing primary particles

52
Q

Ordered mixture (cohesive particles)?

A

Micronised particles adsorbed on surface of larger carrier particles

53
Q

When is segregation likely?

A

Particle size non-uniform
Particle density non-uniform
Spherical shape (free flowing)

54
Q

Demixing - percolation separation

A

Small particles fall through voids

55
Q

Demixing - trajectory segregation

A

Larger particles go further as they have more mass

56
Q

Demixing - elutriation segregation

A

‘Dusting out’ - fine particles settle on top after motion has stopped

57
Q

How to minimise segregation ?

A

Select suitable particle size range
Select excipients to similar density
Reduce vibration

58
Q

What is adsorption due to?

A
  • physical bonding between adsorbent and adsorbate (weak VDW, H-bonds)
  • chemical bonding called chemisorption (via strong covalent bonds)
59
Q

Thin layer chromatography phases?

A

Stationary - silica (polar)

Mobile - liquid mixture of solvents

60
Q

High performance liquid chromatography (HPLC) phases?

A

Mobile - runs through column of solid stationary phase at high pressure

61
Q

Gas chromatography phases?

A

Mobil - has

Stationary - either liquid/solid

62
Q

Alfa tor’s affecting adsorption

A

Temperature (increase temp, decrease adsorption)
Concentration
Nature of solvent
Solute
2nd solid present
pH - many materials ionisable/tendency to interact greatly if exist as polar ions

63
Q

Example of good adsorbent and it’s use?

A

Activated charcoal for overdose/poisoning

-large SA (50-100g adult)

64
Q

What is koalin drug?

A

Adsorb toxins and often used for mild diarrhoea

65
Q

What is chemisorption?

A

When chemical bonding between adsorbent and adsorbate on the monolayer on the surface
-irreversible, only arise when chemical bonds
(Eg ammonia synthesis)

66
Q

What is dissolution?

A

Transfer of molecules/ions from solid state into a solution (thermodynamically favourable)

67
Q

What is solubility?

A

Capacity of absolute to dissolve in a solvent

68
Q

Dissolution rate controlled by?

A

Speed of removal of particles from solid surface
Diffusion rate through boundary layer
Stirring/agitation decrease diffusion gradient

69
Q

What happens when a drug has limited water solubility?

A

Dissolution is rate-limiting step to absorption

70
Q

Why is dissolution testing carried out?

A

For quality control - consistency

Predictive testing - assess product stability

71
Q

How much drug needs to dissolve in QC dissolution testing?

A

More than or equal to 80%

72
Q

Dissolution testing apparatus

A

Basket
Paddle
Flow through cell
Reciprocating cylinder

73
Q

Properties of dissolution medium

A

Mustn’t affect drug stability
Easy to prepare
Preferable inorganic
(Eg 0.1M HCL for weakly basic drugs)

74
Q

Class I

A

Soluble at 250mL
More than 90% absorption
(Dissolution >85% in 30mins)

75
Q

Class II

A

Not soluble in 250mL

Absorption >90%

76
Q

Class III

A

Dose soluble in 250mL

Absorption <90%

77
Q

Class IV

A

Not soluble in 250mL

Absorption <90%

78
Q

Class I rate limiting step?

A

Gastric emptying

79
Q

Class II rate limiting step?

A

Dissolution rate or solubility

80
Q

Class III rate limiting step?

A

Membrane permeability + physiology

81
Q

Class IV rate limiting step?

A

Various, including dissolution rate

Pharmacy (11 decks)

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