Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

week 18 > the medicine > Flashcards

the medicine Flashcards

1
Q

What are insoluble surfactants?

A

they are molecules that are absorbed at interfaces

They are not soluble in the bulk phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does langmuir balance used to measure

A

surface pressure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the equation for surface pressure?

A

surface tension of clean film - surface tension of surfactant covered film

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Explain how surface pressure of a film is increased

A

as a barrier is moved closer to the float
Surfactant monolayer is compressed
Surface tension reduces
Surface pressure increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does Monolayer state

A

That difference surfactants will form different types of absorbed Monolayers at the interface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the monolayer state dependent on?

A

Surfactant structure
The degree the surfactant Layer is compressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the solid or condensed monolayer state

A

surfactant molecules do not cover the full surface
There is a low reduction in surface tension
Therefore, surface pressure is low

If the surfactant molecule cover the full surface
There is a high reduction in surface tension
There is a high surface pressure
(in film compression]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens in liquid state or expanded Monolayers

A

Close, packing into a condensed film is prohibited by bulky side chains or cis configurations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what happens in gaseous state Manolayers

A

It’s results from molecules lying along the surface
Upon compression that is a gradual change in area

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do molecules often show as the film is compressed?

A

Transition from one state to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is a surface acting drug? [surfactant.]

A

A molecule that lowers the surface tension between liquids, or between a liquid and a solid

These drugs are often used to treat conditions that affect the lungs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

how do surfactants work

A

they form a film on the surface of a liquid or a solid. Which helps to reduce the energy required for the liquid or solid to flow.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What information can be gained from measuring surface pressure

A

molecules cross section area
Structural characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what type of monolayer would you expect an alcohol with a cis double bond configuration in its hydrocarbon chain form

A

an expanded monolayer

Close, packing of the molecule is prohibited by the hydrocarbon chain configuration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What does solid/liquid interfacial tension influence

A

The wetting of solids
Determines the contact of the solvent with a particle mass
For example, the penetration of water into a tablet

Influences the loss of drug two containers and solid particulate s

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the possible outcomes of a high interfacial tension and poor wetting

A

A homogenous distribution spread out evenly
High interfacial tension between solid and liquid leads to
an uneven distribution
Solid sticks together or two container to reduce contact with the aqueous phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what does poor wetting lead to

A

tablet/granules/powder in an aqueous phase, trying to reduce contact with this aqueous phase

This can cause: air to be trapped at the solid surface

Poor tablet break down in the stomach

Powders/particles in the suspension clumping together or sticking to the container

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How is wet ability of a solid measured

A

contact angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What does a higher contact angle mean?

A

The higher, the interfacial tension

no wetting

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

when is there complete wetting

A

0 degree contact angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

factors affecting contact angles and wetting

A

crystallization techniques
Using surfactant. [wetting agents]

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

describe surfactant as wetting agents

A

surfactant can be used to lower the solid and liquid interfacial tension

this reduces the contact angle

This aids, the displacing of air at the surface of the solid and improves solid and liquid contact

This helps with wetting if the solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what does the adsorption of surfactant at the solid/liquid interphase look like

A

surfactant can be adsorbed at the solid/liquid interface
the surfactants hydrophobic, tail binds by Vandewal, is forces to the hydrophobic surface of the solid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

I need drugs suspension is to be formulated. The suspension particle has a contact angle of 120°. What problems regarding the suspension stability can you predict

A

The particles will have a high surface/liquid interfacial tension

poor wettability

The suspension will be unstable

To avoid these problems :
The particles can adsorb at the solid liquid interface

This reduces surface tension

This promotes solid and liquid contact and reduces the contact angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What does high interfacial tension between a solid and liquid result in
adsorption of the surfactant molecules [due to the surfactant, hydrophobic tail binding to the hydrophobic surface of a solid.] adsorption of solid particles [solid solid, hydrophobic interactions]
26
is adsorption at the solid/liquid interface, an exothermic or an endothermic process
an exothermic process, as heat is released as the adsorption occurs
27
solid/solid interactions can lead to the adsorption of a drug in solution onto
A solid particulate system A container wall Both reduces contact with the aqueous face
28
what are some problems associated with? adsorption
adsorption of drugs to the container walls and infusion bags Taking drugs simultaneously with antacids
29
what does an increase in Surface area have on the rate of adsorption
increases
30
what does increasing solubility have on the rate of adsorption
Decreases
31
what does an increase in temperature have on the rate of adsorption.
decreases as adsorption is an exothermic process
32
when does maximum adsorption of a drug usually occur
when the drug is completely uniodized Because it is less soluble [hydrophobic] and has the affinity for packing with similar properties
33
what does increasing the drug concentration have on the rate of adsorption
increases
34
what is the langmuir theory
if no more than a single monolayer, of solute is adsorbed onto an absorbent then plotting C/N against C where C= equilibrium concentration of the solute N= number of moles per gram of solid absorbed by the adsorbent This will give a straight line
35
what does the value of Nm give
it is a measure of the adsorbtive capacity of the adsorbent for a particular solute
36
What is the solid/gas interface
influence by similar factors to those of the solid/liquid interface Isotherms used for the solid/liquid interface adsorption were first developed for the solid/gas adsorption
37
how is adsorption at the solid/liquid interface be exploited pharmaceutically
The adsorption of toxins onto activated charcoal
38
give an example where the adsorption at the solid/liquid into face would be of pharmaceutical concern
if a drug is adsorbed to a container and packaging. Therefore, reducing the patient dose
39
What is an electrical double layer
when a solid surface is in contact with a liquid, an electrical charge will be produced at this surface This electrical charge will result in the surface being covered in a layer of surrounding attracted ions [an electrical Leah] This electrical layer has two regions
40
Why do solid surfaces become charged?
due to the ionization of groups at the surface of the particle, in particular atom for example COOH NH3 adsorption of a particular ionic species present in the solution [for example, in water, for hydration to a car hydroxide ions are adsorbed]
41
how is an electrical? Double layer formed
The charge at the solid surface will influence the distribution of surrounding ions in liquid Ions of the opposite charge. [con to ions] are attracted to the solid. Ions of the same charge [:co ions] are repelled
42
what is the fixed layer
solid positivity atom is surrounded by a LAYER of oppositely charged ions Ions of the opposite charge will become fixed to the surface of the particle
43
what is the diffuse Layer
A second layer forms This extending out into the liquid until the charge of the particle no longer influences the distribution of ions
44
What are the four regions to the double layer?
The surface potential The stern layer the surface of shear the zeta potential
45
what is the stern plane
middle of the fixed layer
46
what is the particle surface
The surface of the particle
47
what is the surface of the shear
the outermost layer of the fixed layer
48
regardless of the passcode being positively or negatively, charged, what is the order of potential’s from most positive to least positive
Surface potential stern potential zeta potential
49
what is the pharmaceutical relevance of the Zeta potential?
Both the surface potential, and stern potential are difficult to measure The nearest experimental approximation to the surface is potential is the zeta potential This is a potential at the surface of the shear This is measured by electrophoresis
50
What are two factors that influence the Zeta potential
electrolytes concentration in the aqueous phase: Increasing the electrolytes concentration decreases the Zeta potential Electrolyte valancey: l
51
Why does increasing the electrolytes concentration in the bulk phase increase the number of electrolytes in the double layer
The concentration of electrolytes, of the double layer is direct a proportional to the number of electrolytes in the bulk phase there are more electrolytes present in the fixed Layer The surface charge will be countered eg goes from +100mV to +30mV the (positive) Zeta potential is reduced
52
What does a positive surface potential mean?
If the electrolytes concentration increases, the zeta potential decreases
53
What is negative surface potential
As electrolytes concentration increases Casita potential also increases
54
what does increasing the electrolyte valency do
reduces zeta potential
55
why does increasing the electrolyte valency reduce the Zeta potential
The more charge the counter ion has The more it masks, the surface potential Therefore, there is more reduction in the zeta potential
56
What are three factors that influence the thickness of the double layer
Surface potential Electrolyte concentration Electrolyte valency
57
describe how surface potential influences the thickness of the double layer
The higher the charge at the surface The larger the electrical, double layer
58
Explain how electrolytes concentration influences the thickness of the double layer
increasing electrolytes concentration increases the double layer thickness Increasing electrolytes valance, he increases the double layer thickness
59
Why does the electrical double layer lead to the repulsion between like particles?
Because the double layers do not like to overlap Close, packing and aggregation of particles surrounded by a double layer is blocked Because the double layers do not like to overlap Therefore the electrical double layer result in electrostatic repulsive forces between a like particles It decays as an exponential function of the distance
60
What is the correlation between the size of the double layer on the distance over which the repulsive force acts?
The bigger the double layer, the greater the distance over which the repulsive force acts
61
The presence of double layered around a particles which are alike with prohibits what
Aggregation of the particles Due to the presence of repulsive electrostatic forces between like particles
62
what is the definition of a colloidal system
consists of at least two discrete phases dispersed phase (particles) continuous phase (water)
63
what is the difference between a colloidal dispersion and a coarse dispersion
The distinguishing feature is based loosely on particle size coarse dispersion is when particles are greater than 0.5um size (pharmaceutical emotions, and suspensions) colloidal (natural or synthetic polymers)
64
what are the 3 classes of colloidal systems
lyophilic colloids lyophobic colloids association colloids
65
what are lyophilic colloids
they are solvent loving They despise spontaneously in the continuous phase They are thermodynamically stable The dispersed phase consist generally of large organic molecules lying within colloidal size range
66
what is the preparation of lyophilic colloids
deform spontaneously when liquid vehicle comes in contact with a solid phase This is due to the high attraction between the dispersed and continuous face
67
what are lyophobic colloids
they are solvent hating Therefore, there is a higher surface tension Material does not disperse spontaneously Dispersed phase generally consists of inorganic particles
68
what is the preparation of lyophilic colloids
dispersion method: coarse particles are reduced in size Condensation method: materials of below colloidal size are caused to aggregate into particles within the size range.
69
what are association colloids
they are formed by surfactant molecules At high concentrations, surfactants can aggregate into association colloids or micelles
70
what three factors may a colloidal particles, be influenced by
Thermal energy [osmotic pressure, diffusion] Gravity [sedimentation] Resistance to motion [viscosity.]
71
what is brownian motion
Random movement of colloidal particles resulting from random, collisions with the molecules of the continuous phase This is influenced by thermal energy
72
how does osmotic pressure equilibrate
colloidal particles are too large to pass through the membrane pores In an attempt to equalize the chemical potential on both sides of the membrane, a net movement of solvent occurs across the membrane
73
how does sedimentation affect colloidal particles
they settle under the influence of gravity as their sizes larger than 0.5um For smaller particles, a centrifugal force can be used to sediment the colloidal particles
74
what dictates the method of preparation of colloidal particles, and preparations
The colloidal particles affinity for the continuous phase
75
what candy kinetic properties of colloids be used to calculate
The radius of the colloidal particles
76
What is defined by a suspension?
these are dispersions of an insoluble drug or other substance in an aqueous, or non-aqueous continuous phase
77
What are the pharmaceutical applications of a suspension?
formulation of: An insoluble drug A drug susceptible to degradation Distasteful drugs An increase of drug surface area Topical application
78
What are the typical constituents of pharmaceutical suspensions?
The solvent, plus the drug and generally: wetting agents Compounds to control stability Additives to regulate the flow properties PH regulators Other additives
79
why must the drug be wetted by the liquid
otherwise, separation of the two phases will occur
80
what is an example of a wetting agent
hydrophilic colloids This form a multi molecular coat around the particles
81
What are the four desirable properties of a suspension?
suspended material should not settle rapidly Particles that do settle, should not stick together, or to the bottom of the container. [cake] Particles should resuspend easily when shaken Suspension should not be too viscous for the intended administration route
82
what are Solvents
these are water soluble They reduce interfacial tension They help to displace air from the particle surface
83
What is the definition of a physically stable suspension?
A condition in which the particles do not aggregate, and in which they remain uniformly distributed throughout the dispersion
84
What are the physical stability issues associated with suspensions?
adhesion to the container walls Sedimentation Particle size growth caking Flocculation
85
What is sedimentation?
Where particles collect at the bottom of the container
86
what does decreasing the particle radius do to the rate of sedimentation?
It decreases the rate of sedimentation
87
What does increasing the density due to the rate of sedimentation?
It increases the rate of sedimentation
88
what does increasing the viscosity of the continuous phase due to the rate of sedimentation?
It decreases the rate of sedimentation
89
Does temperature have an effect on the rate of sedimentation?
no
90
Describe particle size growth
Crystal growth can occur on storage This can result from temperature fluctuations [OSTWALD ripening]
91
How do you control Crystal growth?
you use a stable polymorph use a narrow particle size range use wetting agents increase the viscosity of the vehicle If all else fails formulate as a dry powder for reconstitution
92
What is particle size heterogenicity
generally, that will be a particle size range If this is the case, larger particles will settle more rapidly No clear separation boundary is formed This results in zone sedimentation
93
What are examples of density modifiers?
Sucrose, glycerol, or propylene glycol However, this is only effective over a small temperature range
94
what happens when p1=p2
sedimentation does not occur stokes law
95
What are some examples of viscosity modifiers?
Polysaccharides, water soluble celluloses, hydrated silicates
96
what is caking
it is an outcome of sedimentation Sediment particles become cemented together by strong short range forces Particles cannot be re-dispersed It’s arises on the close packing of the sediment particles It cannot be eliminated [only reduced] by particle size reduction, or increasing the viscosity of the continuous phase

week 18 (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions