Disperse System Flashcards
Preparations made up of finely divided solids (suspensoids) distributed uniformly in a liquid vehicle
Suspensions
Size of Suspensoids
> 0.5mcm
Reasons for Formulation of Suspension
Suitable for insoluble solute
Suitable for unstable solute
Mask unpeasant tasting drugs
Properties of Good Suspension
a. Particle size of the suspension should remain fairly constant throughout long periods of undisturbed standing
b. Dispersed particles of the suspension should settle slowly & should be readily redispersed upon gentle shaking of the container
c. The suspension should pour readily & evenly from its container
Types of Suspensions
Gels
Lotions
Emulsions
Semi solid system consisting of suspensions made up of either small inorganic particles or larg organic particles
Gels/Jellies
Types of Gels
Single Phase
Two Phase (Magma/Milk)
Gels in which macromolecules are uniformly distributed throughout a liquid with no apparent boundaries between the dispersed macromolecules and liquid
Single Phase
Single phase Gels are more frequently used in pharmaceutical because
Semisolid State
High degree of clarity
Ease of application and removal
Gel mass consisting of floccules of small distinct particles
Twi Phase / Magma / Milk
Examples of Two Phase Gels
Bentonite Magma - Suspending Agent
Milk of Magnesia - Antacid
A reversible sol-gel/gel-sol formation w/ no charge in volume or temperature,
Thixotropy
Gel takes up the liquid but there is no increase in volume
Imbibition
Gel takes up the liquid but there is increase in volume
Swelling
Gel shrinking
Syneresis
Liquid is removed and only frameworks remain.
Xerogel
Suspension of solids in an aqeuous medium containing one or more active ingredient
For external use
Lotion
Methods of Preparation of Lotions
Trituration
Calamine Lotion, USP (ZnO + Fe2SO3)
Chemical Reactions
White Lotion (ZnSO4 + Sulfurated Potash)
Dispersed systems in which the dispersed phase is composed of small globules of a liquid distributed throughout a vehicle in which it is immiscible.
Emulsion
Components of Emulsions
Dispersed Phase: Internal Phase / Discontinuous Phase
Dispersion Medium: External Phase / Continuous Phase
Emulsifying Agent
Purposes of Emulsions
Increased drug solubility
Increased drug stability
Prolonged drug action
Improved taste
Improved appearance
Types of Emulsion
- Oil in water (o/w)
- Water in oil (w/o)
- Multiple Emulsion – w/o/w or o/w/o
- Microemulsion – transparent; most stable
Oil is dispersed as droplets in an aqueous medium & external washable products
Oil-in-Water (O/W) Emulsion
Used for external preparations when emollient, lubricating, or protective properties are desired
Water-in-Oil (W/O)
Transparent & have droplet diameter in the nanometer size range; Thermodynamically stable
Microemulsion
Factors that determine Emulsion Type
(1) Emulsifier - Some emulsifiers form either w/o or w/o emulsion, others form only one type
(2) Phase Ratio (relative amounts of oil & water) - Phase present in greater concentration tens to be the external phase.
(3) Order of Mixing - The phase that is being added by portions tends to be internal phase
Oil in Water in Tests
Dilution Test: Miscible in Water
Conductivity Test: Yes
Fluorescence Test:No (Dotted Pattern)
CoCl2/FIlter Paper: Blue to Pink
Dye Staining Test: Amaranth
Water-in-Oil Tests
Dilution Test: Miscible in Oil
Conductivity Test: No
Fluorescence Test: Yes
CoCl2/FIlter Paper: No color change
Dye Staining Test: Sudan, Scarlet Red
Emulsion Methods of Preparation
Dry Gum Method
Wet Gum Method
Bottle Method
In Situ Method
Continental Method
Dry Gum Method
English Method
Wet Gum Method
Forbes Bottle Method
Bottle Method
Nascent Soap Method
In Situ Method
Component of Dry Gum Method
Oil: Water: Gum (4:2:1)
Preparation of Dry Gum Method
(Oil + Gum) + Water
Preparation of Dry Gum Method
(Oil + Gum) + Water - added all at once
Mortar & Pestle
Components of Wet Gum Method
Oil: Water: Gum (4:2:1)
Preparation of Wet Gum Method
(Water + Gum) + Oil - Added slowly
Mortar & pestle
Extemporaneous preparation of emulsion from volatile oils or oleaginous substance of low viscosities
Bottle Method
Components of Bottle Method
Oil:Water:Gum (3:2:1 or (2:1:1)
TF: Bottle Method is suitable for high viscous substances
False
Bottle Method is not suitable for high viscous substances
Used to form an o/w or w/o emulsion and is for external use only
In Situ Method
Soap formed in In Situ Method
Soft Soap
Calcium Soaps (Oleic Acid + Lime Water)
Reduce the interfacial tension by forming a film at interface
Emulsifying Agent
