Chapter 14 Disperse systems

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Section 1

Question Answer
dispersed phasesubstance distributed
dispersing mediumvehicle
Dispersed phase + dispersing medium a dispersed or disperse system
Suspensionspreparations containing finely divided drug particles distributed somewhat uniformly throughout a vehicle in which the drug exhibits a minimum degree of solubility.
micropulverizationfine drug powders of about 10 to 50 μm size
Micropulverizersare high-speed attrition or impact mills that are efficient in reducing powders to the size acceptable for most oral and topical suspen- sions.
Rheologythe study of flow, addresses the viscosity characteristics of powders, fluids, and semisolids
Surfactanthave hydrophilic regions (polar head groups) as well as hydrophobic regions (the long hydrophobic chain)
Micelleslipid molecules that arrange themselves in a spherical form in aqueous solutions.
suspensoidfinely divided drug particles
Coarse DispersionsContain particles usually between 10 to 50 μm in size;Include suspensions and emulsions
Fine DispersionsContain particles usually between 0.5 to 10 μm in size;Include magmas and gels.
Colloidal DispersionsContain particles in the colloidal range
Viscosity Characteristicscan be determined by a viscometer
jet millingunder 10 μm size; involves the shearing action of high velocity compressed airstreams in a confined space
Particle SizeMost important single consideration in a discussion of suspensions. Particle diameter should be 1 to 50 μm.
floccule preventing rigid cohesion of small particles of a suspension is intentional formation of a less rigid or loose aggregation of the particles held together by compara- tively weak particle-to-particle bonds

Section 2

Question Answer
emulsion dispersion in which the dis- persed phase is composed of small globules of a liquid distributed throughout a vehicle in which it is immiscible
dispersed phaseinternal phase
dispersing mediumexternal or continuous phase
oil-in-water (o/w)Emulsions with an oleaginous internal phase and an aqueous external phase
water-in-oil (w/o)emulsions having an aqueous internal phase and an oleaginous external phase
Emulsifying Agentsinitial step in preparation of an emulsion is selection of the emulsifier. such as the (natural) occurring agents acacia, tragacanth, agar, chondrus, and pectin and synthetic (anionic,cationc,non-ionic)
Microemulsionsthermodynamically stable, optically transparent isotropic mixtures of a biphasic o/w system stabilized with surfactants.
Hydrophillic-Lipophillic Balanceeach agent is assigned an HLB value or number indicating the substance’s polarity.
Emulsificationprocess involved in making emulsions

Section 3

Question Answer
Continental or Dry Gum Method4:2:1 method because for every 4 parts by volume of oil, 2 parts of water and 1 part of gum are added in preparing the initial or primary emulsion.
English or Wet Gum Methodthe same proportions of oil, water, and gum are used as in the continental or dry gum method,
Bottle or Forbes Bottle Methoduseful for the extemporaneous preparation of emulsions from volatile oils or oleaginous substances of low viscosities.
Auxiliary MethodsAn emulsion prepared by either the wet gum or the dry gum method can generally be increased in quality by passing it through a hand homogenizer.
In Situ Soap MethodThe two types of soaps developed by this method are calcium soaps and soft soaps. Calcium soaps are w/o emulsions that con- tain certain vegetable oils, such as oleic acid, in combination with limewater
Castor Oil Emulsionused as a laxative for isolated occurrences of constipation and in preparation of the colon for radiographic and endoscopic examination
Simethicone Emulsionused as a defoaming agent for the relief of painful symptoms of excessive gas in the gastrointestinal tract.
Gels semisolid systems consisting of dispersions made up of either small inorganic particles or large organic molecules enclosing and interpenetrated by a liquid.
Syneresis occurs when the inter- action between particles of the dispersed phase becomes so great that on standing, the dispersing medium is squeezed out in droplets and the gel shrinks.
inorganic hydrogelsare two- phase systems, such as aluminum hydroxide gel and bentonite magma
organic gelsare single-phase systems and may include such gelling agents as carbomer and tragacanth and those that contain an organic liquid, such as Plastibase.
Bentonite magmapreparation of 5% ben- tonite, a native colloidal hydrated aluminum silicate, in purified water.
Aluminum Hydroxide Gel, USPis an aqueous suspension of a gelatinous precipitate composed of insoluble aluminum hydroxide and the hydrated aluminum oxide, equivalent to about 4% aluminum oxide.
Milk of Magnesiaa preparation containing 7% to 8.5% magnesium hydroxide
aerosolspressurized dosage forms that, upon actuation, emit a fine dispersion of liquid and/or solid materials containing one or more active ingredients in a gaseous medium
metered-dose inhalers (MDIs)Inhalation aerosols that are intended to produce fine particles or droplets for inhalation through the mouth and deposition in the pulmonary tree.
two-phase system aerosol system consists of the liquid phase, contain- ing the liquefied propellant and product concentrate, and the vapor phase.
three-phase system consists of a layer of water-immiscible liquid propellant, a layer of highly aqueous product concentrate, and the vapor phase.
Containers(aerosol)a) glass, uncoated or plastic coated; (b) metal, including tin-plated steel, aluminum, and stainless steel; and (c) plastics.
foamemulsion dosage form containing dispersed gas bubbles. When dispensed, it has a fluffy, semisolid consistency.

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