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Pharmaceutical Emulsion/Emulsion

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Pharmaceutical Emulsion,
As per Syllabus of Mumbai University. Second and First Year B. Pharmacy.

Pharmaceutical Emulsion,
As per Syllabus of Mumbai University. Second and First Year B. Pharmacy.

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Pharmaceutical Emulsion/Emulsion

  1. 1. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 1 EMULSION Syllabus: Definition of ƒ Emulsion, ƒ Emulsifying agent, etc. Types of emulsion, Formulation, Compounding and preservation of Emulsions, Test used for identification of emulsion, Emulsions for external use (Creams). Objectives: Upon completion of this Chapter, you will be able to: Definition of the biphasic dosage forms, Emulsion, Emulsifying agents. Types of emulsion Formulation of emulsion Preservation of emulsions Methods of identification of emulsions. Mr. Pankaj Kusum Ramdas Khuspe M. Pharmacy (Pharmaceutics)
  2. 2. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 2 Definition ÿ Emulsions are, ÿ Heterogeneous, ÿ Thermolabile, ÿ biphasic liquids, ÿ containing two immiscible liquids, ÿ which are made miscible, ÿ By adding emulsifying agent. “Emulsions are heterogeneous, thermolabile biphasic liquids, containing two immiscible liquids which are made miscible by adding emulsifying agent.” Or “Emulsions are a class of dispersed system in which a one immiscible liquid is dispersed uniformly in a liquid dispersion medium.” Or “An emulsion is a dispersion of at least two immiscible liquids, one of which is dispersed as droplets in the other liquid, and stabilized by an emulsifying agent.” ƒ One of which is dispersed as minute globules in to the other. ƒ The liquid which is converted 1. into minute globules is called the “Dispersed Phase” & 2. the liquid in which the globules are dispersed is called the “Continuous Phase.” ƒ Due to a small droplet size of the dispersed phase, the total interfacial area in the emulsion is very large. ƒ Since the creation of interfacial area incurs a positive free energy, the emulsions are thermodynamically unstable and the droplets have the tendency to coalesce. ƒ Therefore, the presence of an energy barrier for stabilizing the droplets is required. ƒ Surfactants reduce the interfacial tension between the immiscible phases; provide a barrier around the droplets as they form; and prevent coalescence of the droplets.
  3. 3. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 3 ƒ Surfactants are mostly used to stabilize emulsions and they are called as emulsifiers or emulsifying agents. ƒ Based on the constituents and the intended application, emulsions may be administered by oral, topical, and parenteral routes. Advantages: 1. Mask the Unpleasant taste. 2. Improved Bio-availability. 3. Sustained Release Medication. 4. Nutritional supplement. 5. Diagnostic purpose (x-rays examination). 6. External use preparation (Cream, Lotion, Foam, Aerosol). Disadvantages: 1. Short shelf-life. 2. Unstable:- soluble phase separate slowly 3. Difficulty in handling 4. Proper Storage required. Types of emulsions: I. Common Emulsions: Two basic types of emulsions are the y Oil-in-water (O/W) emulsion and y Water-in-oil (W/O) emulsion II. Multiple Emulsions: However, depending upon the need, more complex systems referred to as “double emulsions” or “multiple emulsions” can be made. These emulsions have an emulsion as the dispersed phase in a continuous phase and they can be either y Water-in-oil-in-water (W1/O/W2) And y Oil-in-water-in-oil (O1/W/O2) Emulsion. III. By considering particle size: y Macro emulsions: droplets size usually exceeds 10 mm.
  4. 4. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 4 y Mini emulsions: droplets size usually 0.1–10 mm. y Micro emulsions: droplets size usually 100-600 nm. y Nano Emulsions: droplets size usually below 100 nm IV. According to mode of administration: y Oral: Castor Oil, Liquid Paraffin. y External: Creams. y Parenteral: Vitamins. y Rectal: Enema. Formulation of Emulsion: 1. Drug 2. Adjuncts: a. Emulsifier / Emulsifying agents b. Preservatives c. Antioxidants d. Organoleptic Agents I. Coloring agents. II. Flavoring agents. III. Sweetening agents. Emulsifying agents/Emulsifiers: Definition: ƒ Reduce the interfacial tension ƒ Between the immiscible phases; ƒ provide a barrier ƒ around the droplets ƒ Mostly used to stabilize emulsions and ƒ they are called as emulsifiers or emulsifying agents.
  5. 5. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 5 “The substances that reduce the interfacial tension between the immiscible phases; provide a barrier around the droplets and mostly used to stabilize emulsions and they are called as emulsifiers or emulsifying agents.” Or “The substances that reduce the interfacial tension between the immiscible phases; and mostly used to stabilize emulsions and they are called as emulsifiers or emulsifying agents.” Qualities required for good Emulsifying agent: 1.It should reduce surface tension (below 10 dynes/cm). 2.It should be absorbed quickly on surface of dispersed medium. 3.It should form coherent (non-adherent) film. 4.It should be effective in low concentration. 5.It should increase viscosity and maintain consistency. 6.It should be compatible with other ingredients. Classification of emulsifying agents: 1. Natural: a. Vegetable source: Gum acacia, Tragacanth, Agar, Starch, Pectin, Iris Moss. b. Animal source: Wool Fat, Egg Yolk, Gelatin. 2. Semi synthetic: Methyl cellulose, Na CMC 3. Synthetic: a. Anionic: Sodium Lauryl Sulphate b. Cationic: Cetrimide, Benzalkonium chloride. c. Non-ionic: Glyceryl ester- glyceryl monoesters etc. 4. Inorganic: Milk of magnesia, Mg oxide, Mg trioxide etc. 5. Alcohols (polyoles): Carbowax, Cholesterol and Lecithin.
  6. 6. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 6 Selection of Emulsifiers: The Hydrophilic–Lipophilic Balance (HLB) Concept: The selection of different surfactants in the preparation of either O/W or W/O emulsions is often still made on an empirical basis. A semi empirical scale for selecting surfactants is the HLB number developed by Griffin. This scale is based on the relative percentage of hydrophilic to lipophilic (hydrophobic) groups in the surfactant molecule(s). For an O/W emulsion droplet, the hydrophobic chain resides in the oil phase, whereas the hydrophilic head group resides in the aqueous phase. For a W/O emulsion droplet, the hydrophilic group(s) reside in the water droplet, whereas the lipophilic groups reside in the hydrocarbon phase. Table 1.2 gives a guide to the selection of surfactants for a particular application. The HLB number depends on the nature of the oil. As an illustration, Table 1.3 gives the required HLB numbers to emulsify various oils. Table 1.2 Summary of HLB ranges and their applications. Sr. No. HLB RANGE APPLICATION NATURE 1 3-6 W/O emulsifier Hydrophobic 2 7-9 Wetting agent Water Dispersible 3 8-18 O/W emulsifier Hydrophic4 13-15 Detergent 5 15-18 Solubilizer
  7. 7. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 7 Figure No.: 1.3 Griffin Hydrophilic–Lipophilic Balance (HLB) scale. Table 1.3 Required HLB numbers to emulsify various oils. Sr. No. Oil W/O emulsion O/W emulsion 1 Paraffin oil 4 10 2 Beeswax 5 9 3 Linolin, anhydrous 8 12 4 Cyclohexane -- 15 5 Toluene -- 15 The relative importance of the hydrophilic and lipophilic groups was first recognized when using mixtures of surfactants containing varying proportions of a low and high HLB number. The efficiency of any combination (as judged by phase separation) was found to pass a maximum when the blend contained a particular proportion of the surfactant with the higher HLB number. This is illustrated in Figure 1.2 that shows the variation of emulsion stability, droplet size, and interfacial tension with percentage surfactant with high HLB number.
  8. 8. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 8 0 % Surfactant with high HLB 100 Figure No: 1.2: Variation of emulsion stability, droplet size, and interfacial tension with percentage surfactant with high HLB number. The average HLB number may be calculated from additivity HLB = x1HLB1 + x2HLB2 Where: x1 and x2 are the weigh fractions of the two surfactants with HLB1 and HLB2. Natural emulsifying agents a. Vegetable source: i. Acacia: n Emulsion is attractive, palatable and stable in ph 2-5. n Preferred in o/w type of emulsion. n Low viscosity and form multimoleculer film around globules. ii. Tragacanth: n Produce coarse, thick emulsion so rarely used. n Improve viscosity so used in combination with acacia. iii. Agar: n It is not a good emulsifying agent. n It form very thick and viscous emulsion. Droplet size Interfacial tension Emulsion Stability
  9. 9. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 9 n 2% of mucilage used prepared from it. iv. Pectin: n 1% mucilage in water used as EA. n It is incompatible with alkalis, strong alcohol, tannic acid and salicylic acid. v. Starch: n It is rarely used as it form coarse emulsion. n It is used in preparation of enemas. vi. Iris moss (chondrus): n Thickening agent. n Used in combination with acacia in cod-liver oil emulsion. n Concentration of 3% used as EA. b. Animal source: i. Wool fat: n Prepare external use emulsion, absorb 50% of water. n Produce o/w type of emulsion. ii. Egg yolk: n Prepare internal use emulsion. n Preservation in refrigerator. n It used concentration of 12 to 15% iii. Gelatin: n Used for emulsification of liquid paraffin emulsion. n It produces white and agreeable taste emulsion. n Concentration 1%, require preservation. Semi-Synthetic Emulsifying agent a. Methyl cellulose: n It is synthetic derivative of cellulose. n It is used as suspending/thickening agent. n Concentration of 2%. n It form precipitate with electrolytes. b. Sodium Carboxy Methyl Cellulose: n It is used as emulsion stabilizer.
  10. 10. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 10 n It is used as suspending/thickening agent. n Concentration of 0.5 to 1.0 %. Synthetic emulsifying agents a. Anionic: § These are used in the preparation of external use emulsion. § Ex. Alkali soap, metallic soap, sulphated alcohol, sulphonets. § Sodium lauryl sulphate is sulphonated alcohol produces o/w emulsion and form monomolecular film. b. Cationic: § Quaternary ammonium compound e.g. benzalkonium chloride, cetrimide. § Prepare external use preparation. c. Non-ionic: § Glyceryl mono stearate, sorbitan monopalmitate. § Stable over wide range of pH, form multimolecular film. Inorganic emulsifying agent a. Milk of magnesia: n 10 to 20%, prepare o/w coarse emulsion. b. Magnesium oxide: n 5 to 10%, prepare o/w coarse emulsion. c. Magnesium aluminium silicate: n 1% used to prepare o/w coarse emulsion. d. Bentonite: n 5% is used to prepare o/w or w/o emulsion. n When used in o/w emulsion oil is added to the suspension of bentonite. n for w/o emulsion oil is placed in bottle and suspension of bentonite is added. Alcohols / Polyoles a. Carbowaxes(polyethylene glycol): n Used to prepare cream and ointment. n Molecular wt 200-700 viscous, light coloured, hygroscopic liquid.
  11. 11. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 11 n Molecular wt 1000 and above are wax solid. b. Cholesterol: n Ex. Cetyl alcohol, stearyl alcohol, cholesterol. n These are used to stabilize emulsion. c. Lecithin: n It form w/o emulsion. n They are rarely used as they darken the preparation. Breakdown Processes in Emulsions: The various breakdown processes are illustrated in Figure NO: 1. The physical phenomena involved in each breakdown process are not simple, and it requires analysis of the various surface forces involved. In addition, the above-mentioned processes may take place simultaneously rather than consecutively and this complicates the analysis. Model emulsions, with mono disperse droplets, cannot be easily produced, and hence, any theoretical treatment must take into account the effect of droplet size distribution. Theories that take into account the polydispersity of the system are complex, and in many cases, only numerical solutions are possible. In addition, measurements of surfactant and polymer adsorption in an emulsion are not easy and one has to extract such information from measurement at a planer interface. In the following sections, a summary of each of the above-mentioned breakdown processes and details of each process and methods of its prevention are given Creaming and Sedimentation: This process results from external forces usually gravitational or centrifugal. When such forces exceed the thermal motion of the droplets (Brownain motion), a concentration gradient builds up in the system with the larger droplets moving faster to the top (if their density is lower than that of the medium) or to the bottom (if their density is larger than that of the medium) of the container. In the limiting cases, the droplets may form a close-packed (random or ordered) array at the top or bottom of the system with the remainder of the volume occupied by the continuous liquid phase.
  12. 12. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 12 Factor affecting creaming: 1. Radius of globules. 2. Density of dispersion medium/dispersing medium. 3. Viscosity. 4. Storage condition. For these Stokes law is also considered; Stock law: V = 2r2 (d1- d2) g 9µ Where: V: Rate of sedimentation. r: Radius of Globule d1 & d2: Density of dispersion phase & dispersion medium g: Gravitational force µ: Viscosity of medium. Cracking Cracking causes Greater destruction to an emulsion than creaming. It is the coalescence of the globules of internal phase and separation of those phases in to a distinct layer. This is irreversible, since the protective sheet above the globules of the internal phase no longer exists. Re-stabilization by shaking is normally unsuccessful. Reasons for cracking: 1. Addition of opposite charged emulsifying agent. 2. Decomposition/precipitation of emulsifying agent. 3. Addition of common solvent. 4. Microorganism. 5. Change in temperature. Flocculation This process refers to aggregation of the droplets (without any change in primary droplet size) into larger units.
  13. 13. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 13 It is the result of the van der Waals attraction that is universal with all disperse systems. Flocculation occurs when there is not sufficient repulsion to keep the droplets apart to distances where the van der Waals attraction is weak. Flocculation may be ‘‘strong’’ or ‘‘weak,’’ depending on the magnitude of the attractive energy involved. Ostwald Ripening (Disproportionation) This results from the finite solubility of the liquid phases. Liquids that are referred to as being immiscible often have mutual solubilities that are not negligible. With emulsions, which are usually polydisperse, the smaller droplets will have larger solubility when compared with the larger ones (due to curvature effects). With time, the smaller droplets disappear and their molecules diffuse to the bulk and become deposited on the larger droplets. With time, the droplet size distribution shifts to larger values. Coalescence This refers to the process of thinning and disruption of the liquid film between the droplets with the result of fusion of two or more droplets into larger ones. The limiting case for coalescence is the complete separation of the emulsion into two distinct liquid phases. The driving force for coalescence is the surface or film fluctuations which results in close approach of the droplets whereby the van der Waals forces is strong thus preventing their separation. Phase Inversion This refers to the process whereby there will be an exchange between the disperse phase and the medium. For example, an O/W emulsion may with time or change of conditions invert to a W/O emulsion. In many cases, phase inversion passes through a transition state whereby multiple emulsions are produced.
  14. 14. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 14
  15. 15. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 15 Figure No1: Various Schematic representation of the various breakdown processes in emulsions Identification tests for Emulsion 1. Dilution test 2. Fluorescence test 3. Conductivity test 4. Dye test 5. Cobalt chloride paper test SEDIMENTATION FLUCCULATION CREAMING COALESCENCE OSTWALDS RIPENINGPHASE INVERSION
  16. 16. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 16 1. Dilution test/ Miscibility test: 1. Emulsion will remain stable by the addition of external phase. 2. When water is added in to a test tube containing emulsion, if separation of oil globules not occurs, the emulsion is o/w type. 3. If the same is with oil, the separation of oil globules takes place leading to phase separation of the emulsion. 2. Fluorescence test : 1. There are many oils which glow in presence of UV light. 2. Therefore, when emulsion is observed under microscope, if globules shows glowing then it is concluded that the preparation is o/w type. 3. Conductivity test: 1. Water is good conductor of electricity and oil is bad conductor of electricity. 2. When electrodes dipped into emulsion and connected to battery.
  17. 17. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 17 3. If bulb glows, the emulsion is o/w, as water is external phase which conduct the electricity. 4. Dye test/ Dye solubility test: 1. The Water soluble dye is mixed to an emulsion and observed under microscope. 2. If the disperse globules appear colorless and the background red. 3. This is o/w type of emulsion. 5. Cobalt chloride paper test: 1. Anhydrous cobalt is blue in color and hydrous cobalt is red or pink in color. 2. When cobalt chloride paper dip in emulsion, if the color change occurs, from blue to red or pink, 3. Preparation contains water as an external phase so, the emulsion is o/w type. O/W Emulsion W/O Emulsion
  18. 18. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 18 Questions asked till date 1) D J J J Best of Luck J J J
  19. 19. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 19 Types of Emulsions 1. Liquid emulsions a. Emulsions for internal use i. Acacia emulsions ii. Methylcellulose emulsions b. Emulsions for rectal use c. Emulsions for external use i. Soap emulsions 1. Alkali Soap emulsion: 2. Ammonium soap emulsion: 3. Lime Soap emulsion (Lime cream type emulsion): d. Miscellaneous emulsions i. Anionic Emulsifying wax emulsions 2. Semi solid emulsions a. Sterol creams b. Soap creams c. Borax creams d. Anionic emulsifying wax creams e. Cationic emulsifying wax creams f. Creams emulsified with Non ionic surfactants
  20. 20. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 20 1. Liquid emulsions a. Emulsions for internal use i. Acacia emulsions: ∑ These are the emulsions prepared by using acacia gum as emulsifying agent. ∑ Unless other specified generally prepared emulsions for internal use are made with acacia gum. ∑ Generally prepared using a pestle and mortar. ∑ First thick primary emulsion is prepared later it is diluted to its required amount by using vehicle. ∑ Methods used for preparation of these types of emulsions are Dry gum method and Wet gum method. Dry gum method Wet gum method 1.Gum+oil 2.Then Water 3. Form Primary emulsion 4.Make up the volume by dilution with vehicle 5. Emulsion 1. Gum+ Water 2.Then Oil 3. Form Primary emulsion 4. Make up the volume by dilution with vehicle 5. Emulsion ii. Methylcellulose emulsions: ∑ These are the emulsions prepared by using methyl cellulose as emulsifying agent. Method of Preparation 1. First mucilage of methylcellulose 2. Then oil is added 3. Finally homogenized to improve its stability
  21. 21. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 21 b. Emulsions for rectal use: These types of emulsions are prepared for rectal use. c. Emulsions for external use i. Soap emulsions ∑ These types of emulsions are prepared by soap as emulsifying agent. ∑ Depending upon different types of soap (Content of soap) used they are classified in to 3 types. 1. Alkali Soap emulsion: ∑ A preformed soap e.g. Soft soap is used as emulsifying agent. ∑ When no quantity is specified the following proportions are suitable: oFor Fixed & Volatile oils: 10 % of the weight of the oils oFor Fats: 20 % of the weight of the oils. 2. Ammonium soap emulsion: ∑ In these type of emulsion ammonium soap is used as emulsifying agent. ∑ Ammonium soap is produced by interaction of fatty acids with ammonia with agitation during preparation of emulsion. 3. Lime Soap emulsion (Lime cream type emulsion): ∑ In these type of emulsion calcium soap is used as emulsifying agent. ∑ A number of creams, lotions & applications are lime creams i.e. w/o emulsions of fixed oils in which calcium soap is used as emulsifying agent. d. Miscellaneous emulsions i. Anionic Emulsifying wax emulsions 2. Semi solid emulsions a. Sterol creams b. Soap creams
  22. 22. Emulsion Mr. Pankaj Kusum Ramdas Khuspe Page 22 c. Borax creams d. Anionic emulsifying wax creams e. Cationic emulsifying wax creams f. Creams emulsified with Non ionic surfactants

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