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Outcomes of this lecture

Outcomes of this lecture. 1- Definition and Classification of Emulsion 2- Pharmaceutical and medical application of Emulsion 3- Theories of Emulsification 4- Formulation of Emulsion 5- Emulsifying agants 6- Stability of suspensions & Quality control. EMULSIONS.

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Outcomes of this lecture

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  1. Outcomes of this lecture 1- Definition and Classification of Emulsion 2- Pharmaceutical and medical application of Emulsion 3- Theories of Emulsification 4- Formulation of Emulsion 5- Emulsifying agants 6- Stability of suspensions & Quality control

  2. EMULSIONS An emulsion is liquid preparation containing two immiscible liquids, one of which is dispersed as globules (dispersed phase = internal phase) in the other liquid (continuous phase = external phase).

  3. To stabilize these droplets, emulsifying agent should be added Microemulsion: Droplets size range 0.01 to 0.1 m m Macroemulsion: Droplets size range approximately 5 m m.

  4. General Types of Pharmaceutical Emulsions: 1) Lotions 2) Liniments 3) Creams 4) Ointments 5) Vitamin drops

  5. Types of Emulsion mm Water Oil Oil-in-water emulsion Water-in-oil emulsion

  6. Primary and secondary emulsion: • Primary emulsion containing one internal phase, for example, oil-in-water emulsion (o/w) and water-in-oil emulsion (w/o). • Secondary emulsion= multiple-emulsion: it contains two internal phase, for instance, o/w/o or w/o/w. It can be used to delay release or to increase the stability of the active compounds.

  7. Multiple Emulsions mm Water Oil Water-in-oil-in-water emulsion Oil-in-water-in-oil emulsion

  8. < 0.5 mm 0.5-1.5 mm 1.5-3 mm >3 mm Emulsion Size

  9. Very few large droplets contain most of the oil Number Distributions Number • < 0.5 mm • 0.5-1.5 mm • 1.5-3 mm • >3 mm

  10. Chemical Composition Interfacial layer. Essential to stabilizing the emulsion Oil Phase. Limited effects on the properties of the emulsion Aqueous Phase. Aqueous chemical reactions affect the interface and hence emulsion stability

  11. Emulsion Type and Means of Detection: using of naked eye, it is very difficult to differentiate between o/w or w/o emulsions. Thus, the four following methods have been used to identify the type if emulsions.

  12. 1) Dilution Test: based on the solubility of external phase of emulsion. - o/w emulsion can be diluted with water. - w/o emulsion can be diluted with oil.

  13. 2) Conductivity Test: water is good conductor of electricity whereas oil is non-conductor. Therefore, continuous phase of water runs electricity more than continuous phase of oil. = Bulb glows with O/W = Bulb doesn’t glow with W/O

  14. 3) Dye-Solubility Test: • Water-soluble dye will dissolve in the aqueous phase. • Oil-soluble dye will dissolve in the oil phase.

  15. What is look like under the microscope after mixing with suitable dye

  16. 4-Fluorescence test: • oils give fluorescence under UV light, while water doesn’t. Therefore, O/W emulsion shows spotty pattern while W/O emulsion fluoresces.

  17. Pharmaceutical applications of emulsions: 1 ) To mask the taste 2) O/W is convenient means of orally administration of water-insoluble liquids 3) O/W emulsion facilitates the absorption of water-insoluble compounds comparing to their oily solution preparations (e.g. vitamins) 4) Oil-soluble drugs can be given parentrally in form of oil-in water emulsion. (e.g Taxol) 5) Emulsion can be used for external application in cosmetic and therapeutic uses.

  18. Theories of Emulsification: • Incase of two immiscible liquids

  19. An explanation of this phenomenon is because of cohesive force between the molecules of each separate liquid exceeds adhesive force between two liquids. This is manifested as interfacial energy or tension at boundary between the liquids. • Therefore, to prevent the coalescence and separation, emulsifying agents have been used.

  20. Types of emulsifying agents: 1) Surface active agent: adsorbed at oil/water interface to form monomolecular film to reduce the interfacial tension 2) Hydrophilic colloids: forming a multimolecular film around the dispersed droplet 3) Finely divided solid particles: they are adsorbed at the interface between two immiscible liquid phases to form particulate film

  21. A- Monomolecular adsorption

  22. In emulsion, the surface area is high to maintain the dispersion of the droplets. Thus, based on the above equation surface free energy becomes high consequently. The only way to keep it low is to reduce the interfacial tension. Surface active agent (SAA) is molecule which have two parts, one is hydrophilic and the other is hydrophobic. Upon the addition of SAA, they tend to form monolayer film at the oil/water interface.

  23. Form monomolecular film

  24. The functions of surface active agents to provide stability to dispersed droplets are as following: 1) Reduction of the interfacial tension 2) Form coherent monolayer to prevent the coalescence of two droplet when they approach each other 3) Provide surface charge which cause repulsion between adjust particles • Combination of surface-active agents is used most frequently. The combination should form film that closely packed and condensed

  25. Classification of Emulsifying surfactants 1) Anionic group 2) Cationic group 3) Amphoteric group 4) Nonionic group

  26. Classification of Emulsifying surfactants

  27. Classification of surfactants • The "tail" of most surfactants are fairly similar, consisting of a hydrocarbon chain, which can be branch, linear, or aromatic. • Fluorosurfactants have fluorocarbon chains. • Siloxane surfactants have siloxane chains.

  28. Classification of surfactants • Most commonly, surfactants are classified according to polar head group. • A non-ionic surfactant has no charge groups in its head. • The head of an ionic surfactant carries a net charge. If the charge is negative, the surfactant is more specifically called anionic; if the charge is positive, it is called cationic. • If a surfactant contains a head with two oppositely charged groups, it is termed zwitterionic.

  29. Anionic • Sulfate, sulfonate, phosphate, and carboxylates. ammonium lauryl sulfate, sodium lauryl sulfate (SDS, sodium dodecyl sulfate, another name for the compound) and the related alkyl-ether sulfates sodium laureth sulfate, also known as sodium lauryl ether sulfate (SLES), and sodium myreth sulfate. • Docusates: dioctyl sodium sulfosuccinate, perfluorooctanesulfonate (PFOS), perfluorobutanesulfonate, linear alkylbenzenesulfonates (LABs).

  30. Anionic • Carboxylates These are the most common surfactants and comprise the alkyl carboxylates (soaps), such as sodium stearate. More specialized species include sodium lauroylsarcosinate and carboxylate-based fluorosurfactants such as perfluorononanoate, perfluorooctanoate (PFOA or PFO).

  31. Cationic head groups • pH-dependent primary, secondary, or tertiary amines: Primary amines become positively charged at pH < 10, secondary amines become charged at pH < 4: • Octenidinedihydrochloride;

  32. Cationic head groups • Permanently charged quaternary ammonium cation: • Alkyltrimethylammonium salts: cetyltrimethylammonium bromide (CTAB) a.k.a. hexadecyltrimethyl ammonium bromide, cetyltrimethylammonium chloride (CTAC • Cetylpyridinium chloride (CPC) • Benzalkonium chloride (BAC) • Benzethonium chloride (BZT) • 5-Bromo-5-nitro-1,3-dioxane • Dimethyldioctadecylammonium chloride • Cetrimonium bromide • Dioctadecyldimethylammonium bromide (DODAB)

  33. Zwitterionic surfactants (amphoteric) • The cationic part is based on primary, secondary, or tertiary amines or quaternary ammonium cations. • The anionic part can be more variable and include sulfonates, as in CHAPS (3-[(3-Cholamidopropyl)dimethylammonio]-1-propanesulfonate). • Other anionic groups are sultaines illustrated by cocamidopropylhydroxysultaine. Betaines, e.g., cocamidopropylbetaine. Phosphates: lecithin

  34. Nonionic surfactant • Many long chain alcohols exhibit some surfactant properties. • Prominent among these are the fatty alcoholscetyl alcohol, stearyl alcohol, and cetostearyl alcohol (consisting predominantly of cetyl and stearyl alcohols), and oleyl alcohol.

  35. Nonionic surfactant • Polyoxyethylene glycol alkyl ethers (Brij): CH3–(CH2)10–16–(O-C2H4)1–25–OH: - Octaethylene glycol monododecyl ether • Pentaethylene glycol monododecyl ether • Polyoxypropylene glycol alkyl ethers: CH3–(CH2)10–16–(O-C3H6)1–25–O

  36. Nonionic surfactant • Glucoside alkyl ethers: CH3–(CH2)10–16–(O-Glucoside)1–3–OH: - Decylglucoside, - Laurylglucoside - Octylglucoside

  37. Nonionic surfactant • Polyoxyethylene glycol octylphenol ethers: C8H17–(C6H4)–(O-C2H4)1–25–OH: Triton X-100 • Polyoxyethylene glycol alkylphenol ethers: C9H19–(C6H4)–(O-C2H4)1–25–OH: • Nonoxynol-9 • Glycerol alkyl esters: - Glyceryllaurate

  38. Nonionic surfactant • Polyoxyethylene glycol sorbitan alkyl esters: Polysorbate • Sorbitan alkyl esters: Spans • Cocamide MEA, cocamide DEA • Dodecyldimethylamine oxide • Block copolymers of polyethylene glycol and polypropylene glycol: Poloxamers • Polyethoxylated tallow amine (POEA).

  39. B- Multimolecular adsorption • Hydrophilic colloids form multimolecular adsorption at the oil/ water interface. They have low effect on the surface tension. • Their main function as emulsion stabilizers is by making coherent multi-molecular film. This film is strong and resists the coalescence. • They have, also, an auxiliary effect by increasing the viscosity of dispersion medium.

  40. Most of the hydrophilic colloids form oil-in-water emulsions. • Some of them can provide electrostatic repulsion like acacia, which contains Arabic acid and proteins (COOH and NH3)

  41. colloids:

  42. C- Solid particle adsorption • Finely divided solid particles are adsorbed at the surface of emulsion droplet to stabilize them. • Those particles are wetted by both oil and water (but not dissolved) and the concentration of these particles form a particulate film that prevent the coalescence.

  43. Particles that are wetted preferentially by water form o/w emulsion, whereas those wetted more by oil form w/o emulsion • Note that they are very rare to use and can affect rheology of the final product • Size of the particle is very important, larger particles can lead to coalescence

  44. Finely divided solids:

  45. Other emulsifying agents • Egg yolk:it contains phospholipids and cholesterol. The main withdraw back is that spoils quickly; therefore, it can’t be used in industry. • Wool fat:anhydrous lanolin, it is used to prepare w/o emulsion for external uses. • Starch:it forms starch mucilage and it is restricted for enemas preparation. • Cholesterol:it has stabilizing action; therefore, another emulsifier should be included.

  46. CRITERIA FOR THE SELECTION OF EMULSIFYING AGENTS An ideal emulsifying agent should posses the following characteristics: • It should be able to reduce the interfacial tension between the two immiscible liquids. • It should be physically and chemically stable, inert and compatible with the other ingredients of the formulation. • It should be completely non irritant and non toxic in the concentrations used. • It should be organoleptically inert i.e. should not impart any colour, odour or taste to the preparation. • It should be able to form a coherent film around the globules of the dispersed phase and should prevent the coalescence of the droplets of the dispersed phase. • It should be able to produce and maintain the required viscosity of the preparation.

  47. Selection of Emulsifying Agents using HLB method A system was developed by William C. Griffin to assist making systemic decisions about the amounts and types of surfactants needed in stable products. The system is called the HLB (hydrophile-lipophile balance) system. HLB RANGE USE 0-3 Antifoaming agents 4-6 W/O emulsifying agent 7-9 Wetting agents 8-18 O/W emulsifying agent 13-15 Detergents 10-18 Solubilizing agents

  48. Emulsifier with low HLB • An emulsifier having a low HLB number indicates that the number of hydrophilic groups present in the molecule is less and it has a lipophillic character. For example, spans generally have low HLB number and they are also oil soluble. Because of their oil soluble character, spans cause the oil phase to predominate and form a w/o emulsion.

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