Pharmaceutics Exam 3

Front 1

Gels

Back 1

-Semisolid system made of organic or inorganic molecules enclosing liquid. The movement of the dispersion media is restricted by an interlacing three-dimensional network of particles.

Front 2

Gel classification
Single phase

Back 2

-Macromolecules are distributed so that no apparent boundaries exist between the dispersed phase and dispersion media, clear
(Organic)(Carbomers/ tragacanth)

Front 3

Gel classification
Two phase

Back 3

-When the gel mass consists of floccules of small and distinctive particle, mostly inorganic, opaque
(Inorganic)(Aluminum hydroxide gel
Bentonite magma)

Front 4

Hydrogel

Back 4

-Dispersion phase is soluble in water
-Organic hydrogels: Pectin paste, Gums, CMC
Inorganic hydrogels: silica

Front 5

Organogel

Back 5

-Dispersion phase is nonaqueous
-Hydrocarbons: Petrolatum
Fats: Lard

Front 6

Stability problems

Back 6

Syneresis: the separation of liquid from a gel. It is caused by interaction between particles in the dispersed phase

Front 7

Carbomer

Back 7

-High molecular weight water soluble polymer of acrylic acid.
-Their viscosity depends on their polymeric composition
-They are used as jelling agent 0.5-2% in water.

Front 8

Preperation
Fresh precipitation:

Back 8

-Microcrystalline particles strongly attract water and form gelatinous particles

Front 9

Preparation
Directly hydrating the dispersed phase into the dispersion medium:

Back 9

-Other agents may be added to water to enhance gel formation: like propylene glycol or propyl gallate

Front 10

Gelling agents

Back 10

-Acacia, alginic acid, bentonite, CMC, colloidal silicon dioxide…

Front 11

Alginic Acid

Back 11

-Gelling agent
-from seaweed
Used as thickening agent in gels (1-5% )
Swells 200-300 times in water

Front 12

Carbopol

Back 12

-Gelling agent
-Resin
-Controlled release tablets, suspension, topical gels.
-0.5-2% pH 2.5-3
-Many grades approved by FDA
-Gel viscosity depends on electrolyte and pH
-Maximum viscosity and clarity is at 7 pH.
-Should be added slowly into the vortex of liquid

Front 13

Carboxymethylcellulose CMC sodium

Back 13

-Gelling agent
-Dispersed in cold water then heated.
-Sensitive to pH due to carboxylate groups

Front 14

Gelatin

Back 14

-Gelling agent
-Dispersed in hot water then cooled to form gels

Front 15

Plastibase, Jelene

Back 15

-Gelling agent
-5% low M Wt Polyethylene, 95% mineral oil heated to 90C then cooled.

Front 16

Bentonite magma NF

Back 16

-5% bentonite in water
-Bentonite can swell x 12 its volume
-Swelling test is required by USP.
-Used as suspending agent
-Alkaline
-Thixotropic gel

Front 17

Aluminum Hydroxide gel, USP

Back 17

-Aqueous suspension of precipitated aluminum
hydroxide and hydrated aluminum oxide.
-Antacid for hyperacidity and peptic ulcers (Amphojel)
-Interact with tetracycline and may adsorb some drugs.

Front 18

Milk of Magnesia

Back 18

-7-8.5% magnesium hydroxide
-Prepared by chemical reaction NaOH + MgSO4 or direct hydration of magnesium hydroxide
-Water may separate upon standing
-Citric acid may be added

Front 19

Pastes

Back 19

-Prepared by fusion or incorporation
-No levigating agent
-It sticks to its place after application
-Should not be applied to hairy parts
-Used to absorb serous secretions
-Zn oxide paste 25% ZnO with white petrolatum.

Front 20

Emulsion

Back 20

-Preparation in which the dispersed phase is composed of small globules of liquid dispersed throughout a vehicle in which it is immiscible.
-Usually require the addition of emulsifying agent
-Dispersed phase: internal phase, discontinuous phase.
-Dispersing phase, dispersion medium, external phase, continuous.

Front 21

Emulsion types o/w

Back 21

-Internal phase: Oil
-External phase: Water
-Nature: Hydrophilic
-Diluted with: Water, aqueous solutions

Front 22

Emulsion types w/o

Back 22

-Internal phase: Water
-External phase: Oil
-Nature: Hydrophobic
-Diluted with: oil-miscible liquids

Front 23

Purpose of emulsification

Back 23

-Relatively stable mixture of 2 immiscible liquids
-Liquid drug as globules, o/w mask taste of oil.
-Increase surface area for absorption
-Liquid dosage form for poorly water soluble drug.
-Irritant substances would be less irritant if dissolved in the internal phase

Front 24

Surface tension theory

Back 24

-Emulsification decease surface tension allows for formation of internal phase droplets

Front 25

Oriented-wedge theory

Back 25

-Emulsifier curves around droplet, form monomer layer, causes the orientation of the 2 liquids based on the emulsifier solubility

Front 26

The plastic or interfacial film

Back 26

-This layer of film absorbed onto drop surface
-The tougher the film the more stable the emulsion

Front 27

Emulsifying and Stabilizing Agent
Carbohydrate materials

Back 27

-Natural gums acacia, microcrystalline cellulose
O/w emulsions

Front 28

Emulsifying and Stabilizing Agent
Proteins

Back 28

-Gelatin, egg yolk
O/w emulsions
-Gelatin emulsions are liquidly

Front 29

Emulsifying and Stabilizing Agent
High MW alcohols

Back 29

-Stearyl alcohol, cetyl alcohol, glyceryl monostearate , stabilizer O/W emulsion.
-Cholesterol, cholesterol derivatives , W/O emulsion.

Front 30

Span

Back 30

-sorbitan esters
EX Sorbitan monostearate (span 60)

Front 31

Tween

Back 31

-Polyoxyethylene sorbitan esters
EX Polyoxyethylene sorbitan monooleate (tween 80)

Front 32

Phase inversion

Back 32

-By increasing the concentration of the internal phase the viscosity increases and then at a point it drops. At this point the inversion happens.

Front 33

HLB

Back 33

-Emulsifying agents have hydrophilic portion and hydrophobic portion one of which is predominant
-1-20
-HLB 3-6 W/O
-HLB 8-18 O/W
-HLB required depends on the oil and type of emulsion.