Suspensions And Emulsions Flashcards
Disperse system in which solid, vehicle-insoluble particles (internal phase) are uniformly suspended by mechanical agitation
Suspensions
also called the external phase or dispersion system
continuous phase
also called the internal phase or dispersed phase
discontinuous phase
In general, three steps in ensuring formulation of suspension:
• Control particle size
• Use of thickeners
• Use of wetting agent
The greater the density, the greater the descent
Sedimentation
Aggregation will determine the type of suspension
Flocculation
To prevent air trapping
Wetting
Type of Suspension system
A. FLOCCULATED SYSTEM
B. DEFLOCCULATED SYSTEM
Particles appear as floccules like tufts of wool with loose fibrous structure
Flocculated System
Flocculated System is also known as
Coagulated or Colloidally Unstable system
Particles settle as a dense sediment, which becomes more compact after a given time interval
Deflocculated System
Deflocculated System is also known as
Peptized or Colloidally Stable system
Methods of Preparation of Suspensions
A. By discipitation method
B. By precipitation method
This process is done by dispersing the finely divided powders in an appropriate liquid vehicle.
Discipitation Method
This is applicable to those drugs in which its solubility is dependent on pH value.
Precipitation effected by changing the pH
Where simple chemistry is involved
By Double Decomposition Method
Factors in Suspension Formulation
1) Type of suspension desired
2) Formulation adjuvant
3) Preparation techniques
MAIN USE: form mechanical sheath or barrier around particles
• Do not reduce interfacial tension
• Differ in viscosity, thus used in high concentration
Protective colloid
increase the viscosity of water by binding water molecules, limiting their mobility or fluidity
Hydrophilic colloids (hydrocolloids)
incompatible with quarternary antibacterial agents and other positively charged ions
Anionic hydrocolloids
incompatible with negatively charged drugs and excipients
Chitosan
Acacia is usually ___% dispersion in water (mucilage).
35%
Acacia viscosity is greatest between pH _____
5 - 9
Tragacanth is usually used as ___% dispersion in water (mucilage).
6%
Tragacanth has an advantage over acacia in that less is needed, and does not contain _____
Oxidase
The viscosity of tragacanth is greatest at pH
5
polymer that is nonionic and stable to heat and light
Methylcellulose
anionic material that is soluble in water
CMC
Clay Group – EXAMPLE:
bentonite, veegum, magnesium aluminum alginate
Suspending Agents that are strongly hydrated and exhibit thixotropy
Clay Group
Official form of bentonite is
5% magma
is hydrated to a greater degree than bentonite
Veegum
Type of mill used for the reduction of solid particles size and for dispersion of suspensions containing poorly wetted solids.
Rotor Stator
These are semi solid systems consisting of fine dispersions made up of either small inorganic particles or large organic molecules, enclosing and interpenetrated by a liquid.
Gels
A suspension that appears as masses of gel, consist of floccules of small, distinct particles.
Magmas and Milks
Mostly contain finely powdered substances that are insoluble in the dispersion medium and dispersing agents.
Lotions
hydrated aluminum silicate clay
Bentonite
aluminum – magnesium silicate
Veegum
thermodynamically unstable two-phase system consisting of at least two immiscible liquids
Emulsions
Purposes of emulsions
1) Increased drug solubility
2) Increased drug stability
3) Prolonged drug action
4) Improved taste
5) Improved appearance
appear as translucent or transparent and have droplet diameter in the nanometer range (100Å - 1000Å)
Microemulsion
mixtures of a biphasic o/w system stabilized with surfactants
Microemulsion
rapid formation of aggregates or emulsion droplets
Coalescence
result of the interaction of relativity weak particles
Flocculation
IV and oral
o/w type
IM
w/o type
help the production of stable dispersion by reducing interfacial tension and then maintaining the separation of the droplets by forming a barrier at the interface
Emulsifying agents
best emulsifying agent for extemporaneously prepared oral emulsion
ACACIA
Increase the viscosity of an emulsion and prevent creaming
TRAGACANTH
Provides good emulsion stabilization in a concentration of 0.5 to 1%
GELATIN
Used as a primary emulsifier with mineral oil and cod liver oil, and yields an o/w emulsion.
Methylcellulose
It tolerates alcohol up to 40%
Carboxymethylcellulose
It is usually between 1 and 20 is allocated to an emulsifying agent and represents the relative proportions of lipophilic and hydrophilic molecule, and produce an o/w emulsion.
HLB number
HLB 3-6 indicate
lipophilic molecule, produce w/o emulsion
HLB 8-18 indicate
hydrophilic molecule, produce o/w emulsion
Antifoaming hlb values
1-3
Emulsifier (w/o) hlb values
3-6
Emulsifier (o/w) hlb values
8-18
Wetting Agents hlb values
7-9
Solubilizers hlb values
15-20
Detergents hlb values
13-16
Equipment for emulsions which produce extremely fine particles for moderately viscous emulsions
ULTRASONIFIER
ideal for slow mixing of finished emulsions which have been prepared by melting of the waxes
MECHANICAL STIRRERS
