1. PRINCIPLES OF COMPOUNDING
Terrick Andey
College of Pharmacy & Pharmaceutical Sciences
Florida A&M University
February 2013

2. EMULSIONS
Definition: a two-phase dispersion in which one liquid is dispersed in the form of small droplets throughout another liquid
Characteristics:
Dispersed liquid=internal or discontinuous phase
Dispersion liquid=external or continuous phase
Types:
Oil-in-water (o/w): dispersed phase=oil; continuous phase-water
Water-in-oil (w/o): dispersed phase=water
continuous phase-oil

3. EMULSIONS
Emulsifying agent: facilitates the mixing of two immiscible liquids
Therefore, an emulsion consists of:
Dispersed phase
Dispersion medium
Emulsifying agent

4. EMULSIONS Emulsifying agents:
MOA: concentrate at and are absorbed onto the oil:water interface to provide a protective barrier around the droplet
Stabilize the emulsion by reducing the interfacial tension of the system
Imparting a charge on droplet surface, reducing physical contact between droplets, and decreasing potential for coalescence

5. EMULSIFYING AGENTS Types of emulsifying agents: Synthetic:
Surfactants: move to a liquid-liquid interface; reduce surface/interfacial tension of system
Have hydrophilic and lipophilic portions
Hydrophilic part: amino, hydroxyl, carboxyl
Lipophilic part: alkyl chain
Classes of surfactants:
Anionic: alkali soaps, amine soaps, detergents
Cationic: benzalkonium chloride
Nonionic: sorbitan esters, glyceryl esters
Natural: derived from plant or animal sources
Form hydrated lypophilic colloid (hydrocolloid)
No effect on interfacial tension
Protective colloid effect; reduces potential for coalescence

6. EMULSIFYING AGENTS Hydrocolloid classification:
Vegetable derivatives (o/w):acacia, tragacanth, agar, pectin carrageenan
Animal derivatives (w/o): gelatin, lanolin, cholesterol, lecithin
Semi-synthetic agents (o/w):methylcellulose, carboxymethylcellulose
Synthetic agents (o/w): carbopols

7. EMULSIFYING AGENTS Finely divided solids: Auxiliary agents:
Form particulate layer around the dispersed particle
Swells in the dispersion medium to increase viscosity and reduce interaction between dispersed droplets
Used as either o/w or w/o emulsifying agents
Examples: bentonite, Veegum®, magnesium hydroxide, aluminium hydroxide, magnesium trisilicate
Auxiliary agents:
Weak emulsifying properties; used in conjunction with other emulsifying agents
Stabilize emulsion by thickening the formulation
Examples: fatty acids (stearic acid), fatty alcohols (steryl or cetyl alcohol), fatty esters (glycerin monostearate)

8. EMULSIONS Uses: In oral formulations
As vehicle for lipophilic drugs (o/w)
To mask bitter taste of drug
To increase oral solubility
To increase bioavailability
As lotions: fluid emulsions for external application
As creams: opaque, soft solids, or thick liquids for external application; consists of agents dissolved/suspended in an emollient bases

9. HYDROPHILE-LIPOPHILE BALANCE
Hydrophile-Lipophile Balance (HLB):
HLB helps in selecting the appropriate emulsifying agent based on the balance between the hydrophilic and lipophilic portions of the emulsifying agent
Has a scale from 1-18
Low HLB few hydrophlic groups on molecule
will have more of a lipophilic character
High HLB many hydrophlic groups on molecule
will have more of a hydrophlic character

10. EMULSIONS – HLB HLB USE 1-3 Antifoaming agents 3-8
Emulsifying agents for w/o emulsion
7-9
Wetting agents
8-16
Emulsifyinng agents for o/w emulsions
13-16
Detergents
15-20
Solubilizing agents

11. EMULSIONS - Preparation
Methods of preparation:
Continental (Dry Gum or 4:2:1) Method
English (Wet Gum) Method
Bottle (Forbes) Method
Beaker Method
Auxiliary Methods

12. EMULSIONS - Preparation
Continental (Dry Gum or 4:2:1) Method
In a dry mortar, the 1 part of emulsifier is triturate with the 4 parts oil until powder is wetted thoroughly
Two (2) parts of water are added all at once, mixture is vigorously and continuously triturated Creamy white primary emulsion forms
Primary emulsion formation is evident by crackling sound during trituration
NB: Trituration is done vigorously in one direction only

13. EMULSIONS - Preparation
Continental (Dry Gum or 4:2:1) Method
Form primary emulsion from 4 parts of oil, 2 parts of water, and 1 part of emulsifier
Example: Mineral Oil Emulsion U.S.P.
Mineral Oil Emulsion U.S.P. Rx
Mineral Oil ml
acacia, fine powder gm
Syrup ml
Vanillin mg
alcohol ml
Purified water, q.s. ad ml
Procedure:
Mix mineral oil and acacia in a dry Wedgwood/porcelain mortar
Add 250 ml water and triturate the mixture vigorously until an emulsion is formed
Dissolve syrup, vanillin, and 50 ml of purified water in alcohol in small portions whilst triturating
Add sufficient purified water to make 1L

14. EMULSIONS - Preparation
English (Wet Gum) Method
Proportion of oil, water and emulsifier can be the same (4:2:1)
However, order of mixing is different
Triturate 1 part of emulsifier with 2 parts of water to form wetted mixture
Add slowly in small portions, the 4 parts of oil while triturating
After all oil is added, triturate mixture for several minutes to form primary emulsion
Light rapid trituration in one direction is needed for a good emulsion

15. EMULSIONS - Preparation
Bottle (Forbes) Method
A variation of dry gum method
Used to prepare emulsions of volatile oils or oleaginous substances of very low viscosities
Not suitable for highly viscous oils; they cannot be agitated sufficiently in a bottle
Procedure:
Place acacia (1 part) in bottle and add 4 parts of oil
Cap bottle and thoroughly shake rapidly with short strokes
Add required amount of water all at one
Shake mixture thoroughly until primary emulsion is formed

16. EMULSIONS - Preparation
Beaker Method
First three methods use hydrocolloid (gum) emulsifiers which are not suitable when using non-gum or synthetic emulsifiers
Not also the method of choice for compounding lotions or creams
The Beaker method is thus preferred is these cases

17. EMULSIONS - Preparation
Beaker Method
All ingredients are divided into water-soluble and oil-soluble groups
Water-soluble ingredients are dissolved in one beaker
Oil-soluble ingredients are dissolved in a separate beaker
Both beaker are heated to about 70°C using a low-temperature hot plate or steam bath
NB: Aqueous phase is heated a few degrees higher than oleaginous phase, since aqueous phase will cool faster
The two beakers are removed from source of heat and the internal phase is slowly added to the external phase while stirring continuously
Produce is allowed to cool to room temperature while stirring

18. EMULSIONS - Uses As ointment bases:
o/w ointment base: water miscible; non-occlusive; non-greasy
Examples: Vanishing cream (stearic acid cream), Hydrophilic ointment, Weobase, Onibase, Multibase, Dermabase.
w/o ointment base: water immiscible; non-water-washable; non-water-absorbable; occlusive, greasy (typically)
Examples: Rose water ointment (Cold cream U.S.P.), Hydrous wool fat (Lanolin)

19. EMULSIONS - Uses Hydrophilic Ointment U.S.P. Rx Methylparaben 0.25 gm
Propylparaben gm
Steryl alcohol 250 gm
White petrolatum 250 gm
Propylene glycol 120 gm
sodium lauryl sulfate 10 gm
Purified water 370 gm
1000 gm
PROCEDURE:
Melt steryl alcohol and white petrolatum on a steam bath up to 75°C
Separately warm Purified water, mixed with methylparaben, propylene glycol, propylparaben, and dissolve sodium lauryl sulfate to dissolve
With both contents dissolved at 75°C, mix the two and stir until the mixture (emulsion) is completely congealed

20. EMULSIONS - Uses Rose water ointment (Cold cream U.S.P.) Rx
Cetyl Esters Wax 125 gm
White Wax 120 gm
Almond Oil 560 gm
Sodium Borate 5gm
Stronger Rose Water 25 gl
Purified Water 165 ml
Rose Oil 0.2 ml
To make about gm
PROCEDURE:
Triturate cetyl esters wax and the white wax, melt them on a steam bath
Add the almond oil and continue heating until the temperature of the mixture reaches 70°C
Dissolve the sodium borate in the purified water and stronger rose water, water to 70°C
Gradually add the warm solution to the melted mixture, stirring rapidly and continuously until it has cooled to about 45°C
Incorporate the rose oil.