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Dosage Forms and Drug Delivery Systems Lec > Disperse Systems > Flashcards

Disperse Systems Flashcards

1
Q

Emulsions are considered as

A

Heterogenous formulations

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2
Q

Composition of the Dispersed Systems

A
  1. Dispersed/Internal Phase
  2. Dispersing/External/Continuous Phase
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3
Q

Suspensions

A

Generally in the range of 0.1 to 10 um
+ not optically clear and will appear cloud y
+ reproducibility and uniformity of dose is difficult due to settling particles
+ electrical double layer

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4
Q

Size of colloid dispersions

A

0.1 nm to 0.5 um

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5
Q

Fine Dispersion size and examples

A

Size: 0.5 um to 10 um
Examples: Suspensions, Emulsions

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6
Q

Coarse Dispersion

A

10 um to 50 um

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7
Q

What is the particle formation in the inner layer for suspensions?

A

tightly packed called the fixed layer

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8
Q

What is the charge formation in the outer layer?

A

Mobile also known as diffuse layer

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9
Q

Synonyms for Fixed Layer

A

Stern Layer

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10
Q

Synonyms for Diffuse Layer

A

Gouy-Chapman Layer

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11
Q

When is a hydrophobic core during the addition of surfactants in suspensions?

A

If CMC is reached

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12
Q

How does surfactants affect the charge of suspensions?

A

Affect based on anionic, cationic, nonionic character
can also promote release of ionic components into diffuse layer

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13
Q

Example of a surfactant releasing ionic components in the diffuse layer

A

Sodium Lauryl Sulfate Releaseing Sodium

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14
Q

Advantages of Suspension

A

Improved Taste
Improved Solubility
Sustaining Effect
Basic Solubility

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15
Q

Requirements for Suspension

A

+ Settle Slowly
+ Easily Dispersed from shaking a container
+ Uniformity for a long amounts of time
+ Readily and evenly poured from its container

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16
Q

How can we achieved the requirements necessary to make a suspension?

A

+ Reducing particle size
+ Make density of vehicle larger than suspenoid
+ Increasing viscosity of vehicle

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17
Q

What can be used to prevent caking as there is a high chance of its occurance in small sized particle dosage forms such as suspensions?

A

Flocculation

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18
Q

How do we produce flocculation?

A

Incorporation of clays
Adjusting pH to minimum range of solubility
adjust nonionic and ionic surfactants

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19
Q

This theory insinuates that the colloidal stability of a given system depends on the relative strengths of the attractive van der Waals and the repulsive electric double-layer interactions

A

Derjaguin, Landau, Vervey, Overbeek Theory (DLVO)

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20
Q

explains the aggregation of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium

A

DLVO Theory

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21
Q

concerned with predicting the stability of lyophobic colloids

A

DLVO Theory

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22
Q

Brownian Movement is exhibited resulting to homogeneity
For particles approx. 1 to 2 um radius

A

Diffusion

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23
Q

For particle approximately 0.5 um
affected by viscosity, gravity, and particle size (flocculated, deflocculated)

A

Sedimentation Rate

24
Q

T/F. Sedimentation rate is directly proportional to diffusion.

A

False. It brings particles together.

25
Q

Factors that affect Sedimentation and Diffusion:

A

+ Reduce Particle Size
+ Density of Particle
+ Density of Medium
+ Viscosity
+ Temperature

26
Q

Examples of polymers that can reduce diffusion to zero

A

HPMC, Sodium CMC

27
Q

Flocculated systems form clear supernatant liquids in

A

minutes, hours, days

28
Q

Differentiate Flocculated Suspensions and Deflocculated suspensions.

A
29
Q

Deflocculated systems create supernatant within

A

days to weeks

30
Q

Displace air, disperse the particles, and allow penetration of the dispersion medium into the powder

A

Wetting agents

31
Q

The ability of a liquid to spread across a solid surface

A

Wettability

32
Q

Solid particles clump together leads to

A

reduced surface tension, and obtain energetically favorable situation

33
Q

Natural consequences of adjusting particles for wetting agents i.e. reducing total particulate SA is reduced

A

+ inhomogenous
+ inelegant
Reproducible dosing is not possible

34
Q

Thicken the dispersion medium and add to its structure, helping suspend
the suspensoid. Can be used as emulsifying agent

A

Suspending agent

35
Q

dispersions of two immiscible (or partially miscible) liquids, one of which is distributed uniformly in the form of fine droplets (the dispersed phase) throughout the other (the continuous phase)

A

Emulsions

36
Q

Advantages of emulsions

A

Improved Bioavailability
Improved palatability and acceptability
reduced side effects
minimize odor of oil - based pharmaceuticals

37
Q

Visual appearnace of an emulsion depends on the

A

Droplet size on light scattering

38
Q

Size of diamer of droplets in IV emulsions

A

not exceeding 5 um

39
Q

Where are dropletes of less than 5 um are cleared from the elements?

A

Reticuloendothelial sysem
Mononuclear phagocyte system

40
Q

Emulsions with o/w type

A

oral and IV

41
Q

W/O type of emulsion

A

Dermatological, IM, SQ

42
Q

Contrast agents that can affect of drugs administered highly acqueous

A

Iodized oils, bromized perfluorocarbon oils

43
Q

delivery systems that are not emulsions in the first place, but become emulsions when they reach the stomach. They are composed of drug, oil(s), surfactants and sometimes co-solvents

A

Self - emulsifying drug delivery systems (SEDDS)

44
Q

What to do sterile intravenous o/w emulsions in hosptials carry?

A

Lipid soluble drugs i.e. calroies and essential FA

45
Q

can be used to prolong the delivery of water-soluble antigens and thus
provide a longer lasting immunity

A

w/o emulsions in IM and SQ routes

46
Q

How to modify the surface properties of emulsions?

A

Control charged nature of interfacial film

47
Q

T/F. Droplet charge provided by the emulsifier film does not influences
the biological rate of the droplets as well as emulsion stability.

A

False. It can

48
Q

Which can be rapidly cleared from positive ones? Negatively charged particles of positively/neutral charged ones.

A

Negatively charged

49
Q

Other advantages of emulsions:

A

*Prolonged drug action
*Improved taste
*Improved patient compliance
*Improved appearance
*Absorption may be enhanced by the diminished size of the internal phase
*Water is an inexpensive diluent

50
Q

Theory of the use of surfactants as emulsifiers and stabilizers, resulting in the lowering of interfacial tension of the 2 immiscible liquids

A

Surface tension theory

51
Q

Surfactants in surface tension theory facilitate

A

breaking of larger globules to smaller ones

52
Q

Assumes monomolecular layers of emulsifying agent curved around a droplet of the internal phase of the emulsion.

A

Oriented-Wedge Theory

53
Q

Plastic - interfacial film theory

A

Places the emulsifying agent at the interface between the oil & water, surrounding the droplets of the internal phase as a thin layer of film adsorbed on the surface of the drops

54
Q

Purposes of films

A

Films can prevent contact and coalescing of dispersed phases.

55
Q

Methods of Preparing Emulsions

A

Dry Gum Method
Wet Gum Method
Forbes Bottle Method

56
Q
A

Dosage Forms and Drug Delivery Systems Lec (5 decks)

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