Disperse Systems Flashcards
Emulsions are considered as
Heterogenous formulations
Composition of the Dispersed Systems
- Dispersed/Internal Phase
- Dispersing/External/Continuous Phase
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
Size of colloid dispersions
0.1 nm to 0.5 um
Fine Dispersion size and examples
Size: 0.5 um to 10 um
Examples: Suspensions, Emulsions
Coarse Dispersion
10 um to 50 um
What is the particle formation in the inner layer for suspensions?
tightly packed called the fixed layer
What is the charge formation in the outer layer?
Mobile also known as diffuse layer
Synonyms for Fixed Layer
Stern Layer
Synonyms for Diffuse Layer
Gouy-Chapman Layer
When is a hydrophobic core during the addition of surfactants in suspensions?
If CMC is reached
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
Example of a surfactant releasing ionic components in the diffuse layer
Sodium Lauryl Sulfate Releaseing Sodium
Advantages of Suspension
Improved Taste
Improved Solubility
Sustaining Effect
Basic Solubility
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
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
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
How do we produce flocculation?
Incorporation of clays
Adjusting pH to minimum range of solubility
adjust nonionic and ionic surfactants
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)
explains the aggregation of aqueous dispersions quantitatively and describes the force between charged surfaces interacting through a liquid medium
DLVO Theory
concerned with predicting the stability of lyophobic colloids
DLVO Theory
Brownian Movement is exhibited resulting to homogeneity
For particles approx. 1 to 2 um radius
Diffusion
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
