Disperse Systems Flashcards by hello world

Emulsions are considered as

Heterogenous formulations

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Composition of the Dispersed Systems

Dispersed/Internal Phase
Dispersing/External/Continuous Phase

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Suspensions

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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Size of colloid dispersions

0.1 nm to 0.5 um

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Fine Dispersion size and examples

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

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Coarse Dispersion

10 um to 50 um

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

tightly packed called the fixed layer

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What is the charge formation in the outer layer?

Mobile also known as diffuse layer

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Synonyms for Fixed Layer

Stern Layer

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Synonyms for Diffuse Layer

Gouy-Chapman Layer

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

If CMC is reached

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How does surfactants affect the charge of suspensions?

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

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Example of a surfactant releasing ionic components in the diffuse layer

Sodium Lauryl Sulfate Releaseing Sodium

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Advantages of Suspension

Improved Taste
Improved Solubility
Sustaining Effect
Basic Solubility

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Requirements for Suspension

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

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

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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?

Flocculation

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How do we produce flocculation?

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

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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

Derjaguin, Landau, Vervey, Overbeek Theory (DLVO)

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

DLVO Theory

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concerned with predicting the stability of lyophobic colloids

DLVO Theory

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

Diffusion

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

Sedimentation Rate

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

False. It brings particles together.

Factors that affect Sedimentation and Diffusion:

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

Examples of polymers that can reduce diffusion to zero

HPMC, Sodium CMC

Flocculated systems form clear supernatant liquids in

minutes, hours, days

Differentiate Flocculated Suspensions and Deflocculated suspensions.

Deflocculated systems create supernatant within

days to weeks

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

Wetting agents

The ability of a liquid to spread across a solid surface

Wettability

Solid particles clump together leads to

reduced surface tension, and obtain energetically favorable situation

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

+ inhomogenous + inelegant Reproducible dosing is not possible

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

Suspending agent

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)

Emulsions

Advantages of emulsions

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

Visual appearnace of an emulsion depends on the

Droplet size on light scattering

Size of diamer of droplets in IV emulsions

not exceeding 5 um

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

Reticuloendothelial sysem Mononuclear phagocyte system

Emulsions with o/w type

oral and IV

W/O type of emulsion

Dermatological, IM, SQ

Contrast agents that can affect of drugs administered highly acqueous

Iodized oils, bromized perfluorocarbon oils

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

Self - emulsifying drug delivery systems (SEDDS)

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

Lipid soluble drugs i.e. calroies and essential FA

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

w/o emulsions in IM and SQ routes

How to modify the surface properties of emulsions?

Control charged nature of interfacial film

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

False. It can

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

Negatively charged

Other advantages of emulsions:

*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

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

Surface tension theory

Surfactants in surface tension theory facilitate

breaking of larger globules to smaller ones

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

Oriented-Wedge Theory

Plastic - interfacial film theory

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

Purposes of films

Films can prevent contact and coalescing of dispersed phases.

Methods of Preparing Emulsions

Dry Gum Method Wet Gum Method Forbes Bottle Method