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Pharmaceutics > Surfactants, Polymers and Drug Delivery > Flashcards

Surfactants, Polymers and Drug Delivery Flashcards

1
Q

the classification of surfactants is based on what empirical system?

A

HLB (hydrophily lipophile balance )

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2
Q

the HLB of surfactants is a measure of the relative contributions of the __ and __ regions

A

hydrophilic and lipophilic

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3
Q

what is the use of the HLB system?

A

helps determine which surfactant to use for specific applications

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4
Q

what are surfactants?

A

compounds with the tendency to accumulate at the interface between two phases

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5
Q

what are the interchangeable terms used for surfactants?

A

ampiphiles, amphipathic, surface-active agents, surfactants

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6
Q

surfactants change the nature of the __

A

interface

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7
Q

a decrease in interfacial tension between oil and water phases results in ___ formation

A

emulsion

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8
Q

surfactants allow for the adsorption of insoluble particles, which enables their dispersion and the formation of __

A

suspension

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9
Q

surfactants can form micelles, which result in __ solution

A

clear

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10
Q

give 2 examples of non-ionic surfactants

A

sorbitan esters and polysorbates

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11
Q

what are sorbitan esters?

A

mixtures of the partial esters of sorbitol and its mono and di-anhydrides with oleic acid

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12
Q

sorbitan esters are __ and used as ___ and __

A

insoluble; wetting agents and emulsifiers

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13
Q

polysorbates are also called __

A

Tweens

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14
Q

polysorbates are ___ with water and are used as ___

A

miscible; oil-in water emulsifier

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15
Q

sodium laurel sulphate BP is an example of what type of surfactant?

A

anionic

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16
Q

sodium lauryl sulphate is a mix of ___, very soluble in __ at rt and is used as a ___ agent in skin cleaner and medicated shampoos

A

sodium alkyl sulphates; water; foaming

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17
Q

quaternary ammonium and pyridium cationic surfactants are examples of which type of surfactant?

A

cationic

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18
Q

quaternary ammonium and pyridium cationic surfactants are used as bactericidal agents against gram __ bacteria and some __ bacteria. They are used to clean __ and __

A

positive, some gram negative; skin of wounds and hospital utensils

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19
Q

surfactants ___ surface and interfacial tension

A

decrease

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20
Q

an increase in surface activity means a __ in surface tension

A

decrease

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21
Q

compounds which are most effective at lowering surface tension are those with a high ___

A

surface activity

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22
Q

there is an equilibrium between surfactant molecules at the surface of the solution and those in the bulk of solution, which is expressed by the __ equation

A

Gibbs

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23
Q

when surfactant is dissolved in water, how will it orientate?

A

at the surface with its hydrophilic parts inward and its hydrophobic bits outward

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24
Q

at the interface between two immiscible solvents, how will a surfactant orientate?

A

with its hydrphillic bits in the aq and its hydrophobic bits in the oil

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25
Q

why does surfactant decrease surface tension when surfactant molecules adsorb at water? what force is reduced?

A

the surfactant molecules replace some of the water molecules in the surface and the forces of attraction between surfactant and water are less that water on water. Contraction force is reduced

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26
Q

what is adsorption?

A

process of accumulation at an interface; essential a surface effect that is different than absorption

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27
Q

what is physical adsorption?

A

the adsorbate is bound to the surface by weak van Der Waals forces that can be reversed

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28
Q

chemical adsorption / chemisorption involves ___ valence forces than that of physical adsorption

A

stronger

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29
Q

which type of adsorption is more specific?

A

chemisorption

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30
Q

chemisorption usually involves a ___ process

A

ion exchange

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31
Q

is it possible to have both physical and chemisorption involved an adsorption process?

A

yes

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32
Q

give an example of adsorption process that uses both physical and chemical adsorption and explain each contribution

A

Ex: adsorption of toxin in the stomach by attagpulgite and kaolin

Chemisorption: cation exchange with the basic groups of toxins
Physical: adsorption of the rest of the molecule

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33
Q

micelles are formed at the __

A

critical micelle concentration

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34
Q

CMC is reached at what point?

A

inflection point when surface tension is plotted against concentration

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35
Q

most micelles are ___ in shape and consist of __ to ___ surfactant molecules

A

spherical; 60-100

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36
Q

micelles are used to stabilize __ drugs

A

water-insoluble

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37
Q

list 4 applications of adsorption as pharmaceutical applications

A
  1. adsorption of toxins/poisons
  2. taste masking
  3. hemoperfusion
  4. adsorption in drug formulation
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38
Q

adsorption of toxins employs universal antidotes, provide 3 examples of these

A
  1. activated charcoal
  2. magnesium oxide
  3. tannic acid
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39
Q

taste masking by adsorption is often employed for what prescription drug?

A

diazepam

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40
Q

what must be considered when using adsorption to mask taste problems in oral drugs?

A

need to be careful that you don’t use so much surfactant that it decreases the efficacy of the drug

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41
Q

carbon hemoperfusion is used for treatment of what?

A

severe drug overdose

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42
Q

adsorption of surfactants onto poorly soluble solids ___ the wetting and dissolution rate

A

increases

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43
Q

the typical size of a micelle is ___nm, therefore __ visible under microscope

A

2-3; not

44
Q

a __ exists between micelles and free surfactant molecules in solution

A

equilibrium

45
Q

when surfactant concentration is increased above the CMC, the number of ___ increases, bit ___ stays the same at the CMC value

A

micelles; free surfactant concentration

46
Q

when considering solubility in terms of surfactants, you think of the amount needed to _____ in order to promote dissolution

A

arrange around insoluble molecule

47
Q

increase in surfactant results in a __ in surface tension

A

decrease

48
Q

what happens at the CMC inflection point?

A

all insoluble molecules will be in micelles and a clear solution will be produced

49
Q

at high electrolyte concentrations, the micelles of ___ surfactants may become non-spherical, leading to precipitation of the compound

A

ionic

50
Q

what is solubilization?

A

process whereby water-insoluble substance are brought together into solution by incorporation into micelles

51
Q

solubilization is affected by what 3 factprs?

A
  1. temperature
  2. nature of solubilisate
  3. nature of surfactants
52
Q

what is the solubilization site for non-polar compounds?

A

the aliphatic hydrocarbons dissolve in the hydrocarbon core of ionic and non-ions micelles

53
Q

what is the solubilization site for polar compounds?

A

the polar group will be at the core-surface interface with the hydrophobic part buried in the core

54
Q

the properties of a surfactant are determined by the balance between the __and _ parts of the molecule

A

hydrophobic and hydrophilic

55
Q

if the hydrophilic chain length is increased, what happens to the CMC?

A

it increases bc the molecule is more hydrophilic

56
Q

if the hydrophobic chai length is increased, what happens to the CMC?

A

it is decreased (micelles form at lower solution concentration)

57
Q

electrolyte addition to solution of ionic surfactants ___ CMC and __ micelle size

A

decreases; increases

58
Q

give examples of solubilization of phenolic compounds

A

cresol, chlorrcresol, chloroxylenol and thymol with soap to form clear solutions for disinfecting

59
Q

provide an example of solubilization of iodine in non-ionic surfactant micelle

A

iodophors used in sterilization n

60
Q

provide examples of solubilization of drugs

A

steroids and water-insoluble vitamins, by non-ionic surfactants (usually polysorbates or polyethylene sorbitan esters of fatty acids

61
Q

what are polymers?

A

high compounds of high molecular weight with repeating monomer units

62
Q

extensive cross-linking of a polymer makes it __ soluble l

A

less

63
Q

if the monomer units are identical, the polymer is called

A

homopolymer

64
Q

polymers formed of more than one type are called __

A

copolymers

65
Q

the MW of polymers is a ___ MW, based on __

A

average; experimental method

66
Q

what is polydispersity?

A

in solution, there are usually a range of sizes of polymer chains

67
Q

the average molecular weight is biased towards __

A

large molecules

68
Q

the viscosity of a polymer depends on what 4 things?

A
  1. concentration
  2. polymer-solvent interactions
  3. charge interactions
  4. binding of small molecules
69
Q

the viscosity of ionized polymers is complicated by ___ which vary with polymer concentration and addictive concentration

A

charge interactions

70
Q

the arrangement of the copolymer has effects on ___ properties

A

physical

71
Q

polymer gels are __ and may form __ in aqueous soon

A

surfactants; micelles

72
Q

at high concentrations of polymer gel, the micelles can pack so tightly that __

A

the solution becomes immobile (gelation occurs)

73
Q

gelation of a polymer gel may occur due to what type of temperature change? why is this?

A

warming; because the solubility of poly(oxyethylene) decreases

74
Q

as temperature increases, polymer gels become more _

A

hydrophobic

75
Q

in polymer gels, a 3-D polymer-solvent systen network can be formed by __ or __

A

swelling of solid polymer; reduction in solubility of polymer in sole

76
Q

when gels are formed from soln, each system is characterized by a ___, below which gelation will not occur

A

critical concentration of gelation

77
Q

gelation is characterized by a large increase in __ beyond the ___ point

A

viscosity; gel

78
Q

gels have what physical characteristics?

A

elasticity, and rubber-like

79
Q

gels can be reversible or irreversible based on __

A

the bonds between chains of the network

80
Q

what is Gum arabic and its characteristics and application?

A

1) very soluble polyelectrolyte
2) highly viscous due to branched structure of the macromolecule chains
3. used as emulsifier

81
Q

what is gum tragacanth, its characteristics an application?

A

1) gum
2) partially dissolves in water to give highly viscous sol
3) natural emulsifier and thickener, effective a suspending agent

82
Q

what are alginates, their characteristics and application?

A
  1. block co-polymer polysaccharides derived fro seaweed consisting of B-D-mannuronic acid and a-L-guluronic acid residues joined by 1,4 glycosidic bonds
  2. very viscous and gel on addition of acid or calcium salts
  3. stabilizers and thickening agents
83
Q

what are 3 families of water-soluble polymers?

A

carboxypolymethylene
cellulose derivatives
natural gums and mucilages

84
Q

what are the applications of carbomer and carbopol?

A
  1. suspending agents

2. binders in prolonged and immediate action tablets

85
Q

what is an application for low-viscosity methyl cellulose?

A

emulsifier

86
Q

what is an application for high-viscosity methyl cellulose

A

thickening agent

87
Q

what is an application for hydroxypropylmethylicellulose?

A

viscous colloidal solo for eye drops and artificial tears

88
Q

water insoluble polymers are affected by what 3 characteristics?

A
  1. degree of crystallinity
  2. permeability to drugs
  3. permeability to gases
89
Q

what effect does the degree of crystallinity have on water-insoluble polymers?

A

affects rigidity, fluidity, resistance to diffusion of small molecules and degradation

90
Q

drug diffusion is governed by ___ and affected by __, __and __

A

Ficks Law,; crystallinity, solubility, and method of preparation

91
Q

water insoluble polymers are typically used for __

A

making membranes, containers and tubing

92
Q

silicones are ___ polymers with a structure containing alternate forma of __ and __

A

water-insoluble; Si and O

93
Q

dimeticones are a type of __ that are used as ___ substances to protect skin against __

A

silicone; barrier substance/water repellent; water-soluble irritants

94
Q

Dimeticine 200 is used a lubricant for __ and to replace degenerative ___ in cases of retinal detachment

A

artificial eyes; vitreous fluid

95
Q

dimeticone can act as a lubricant for simple __

A

joints

96
Q

what is activated dimeticone (activated polymethylsiloxane) ?

A

a mix of liquid dimeticones containing finely divided silica to enhance the defaming properties of the silicone

97
Q

simethicone is used as a __

A

anti-flatulent / reduce bloating

98
Q

steroids have an affinity for __ tubing

A

polyethylene

99
Q

Glyceryl trinitrate has a high affinity for __ plastics, and can leave tablets, reducing the active content to __

A

lipophilic ; zero

100
Q

explain ion exchange properties of water-insoluble polymers

A

attached ionizable groups can exchange with ions attracted to their ionized groups

101
Q

give an example of anion exchange in water-insoluble polymers application

A

polyamide methylene resin and polyaminostyrene used as antacids

102
Q

give an example of cation exchange in water-insoluble polymers application

A

calcium and sodium forms used to treat hyperkalaemia

103
Q

evaporated polymer films leave a __ on tablets

A

protective coating

104
Q

what are the 3 types of matrices?

A
  1. non-eroding
  2. reservoir system
  3. eroding matrix
105
Q

what are microcapsules?

A

drug encapsulated as small particles or as a drug soln in a polymer oil or coat

106
Q

what are microspheres?

A

solid polymeric spheres which entrap drug

107
Q

what are nano capsules and nanoparticles ?

A

structures equivalent to microspheres and capsules, ranging in size from 50 - 500 nm

Pharmaceutics (2 decks)

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