Emulsion (Physical Pharmacy) PDF

EMULSIONS  Emulsions 1) DEFINITION. 2) TYPES OF EMULSIONS. 3) ADVANTAGES/ DISADVANTAGES. 5) EMULSIFYING AGENTS. 6) TYPES OF EMULSIFYING AGENTS. 7) THEORIES OF EMULSIFICATION. 8) PREPARATION OF EMULSIONS. 9) STABILITY OF EMULSIONS.  DEFINITION  An Emulsion is a mixture of two or more liq...

EMULSIONS  Emulsions 1) DEFINITION. 2) TYPES OF EMULSIONS. 3) ADVANTAGES/ DISADVANTAGES. 5) EMULSIFYING AGENTS. 6) TYPES OF EMULSIFYING AGENTS. 7) THEORIES OF EMULSIFICATION. 8) PREPARATION OF EMULSIONS. 9) STABILITY OF EMULSIONS.  DEFINITION  An Emulsion is a mixture of two or more liquids that are normally Immiscible. Oil Oil Agitation Oil Water Water Water Separate rapidly into two clear defined layers  Emulsion, is a thermodynamically unstable system consisting of two immiscible liquids in which one liquid is dispersed as fine globule throughout the other with the help of emulsifying agents. INTERNAL PHASE OR EXTERNAL PHASE IN EMULSIONS:  The dispersed liquid is known as the Internal or Discontinuous phase.  whereas the dispersion medium is known as the External or Continuous phase.  TYPES OF EMULSIONS Based on dispersed phase:  Oil in Water (O/W): Oil droplets dispersed in water.  Water in Oil (W/O): Water droplets dispersed in oil.  Water in Oil in water (W/O/W): Water in Oil emulsion dispersed in water – multiple emulsion. Based on size of liquid droplets:  0.2 – 50 mm Macroemulsions  0.01 – 0.2 mm Microemulsions TYPES OF EMULSION  Simple emulsions (Macro emulsions)  Oil-in-water (O/W)  Water-in-oil (W/O)  Multiple emulsions  Oil-in-water-in-oil (O/W/O)  Water-in-oil-in-water (W/O/W)  Micro emulsions TYPES OF EMUSLION Micro emulsions Nano emulsions Multiple Simple emulsions emulsions - Oil-in-water-in- Thermodynam (Macro emulsions) oil (O/W/O) ically stable Water-in-oil-in- optically Oil-in-water water transparent , (O/W) (W/O/W) Water-in-oil -(W/O) diameter greater than 0.1 μm GENERAL TYPES OF PHARMACEUTICAL EMULSIONS Lotions Linime -nts Vitamin drops Emulsions Creams Ointm- ents  ADVANTAGES OF EMULSIONS:  Mask the unpleasant taste O/W is convenient means of oral administration of water-insoluble liquids.  Oil-soluble drugs can be given parentrally in form of oil- in water emulsion. (e.g Taxol).  Emulsion can be used for external application in cosmetic and therapeutic Application because of Better and faster absorption.  Sustained release medication.  Nutritional supplement.  Inert and chemically non-reactive.  Reasonably odorless and cost Effective.  DISADVANTAGES OF EMULSIONS:  Emulsions are thermodynamically unstable and have short shelf-life.  Improper formulation of emulsions leads to creaming and cracking of emulsion.  Improper selection of emulsifying agent leads to phase inversion and some times it may also lead to cracking. DIFFERENCE BETWEEN O/W AND W/O EMULSIONS Water in oil emulsion (w/o) Oil in water emulsion (o/w) Oil is the dispersion medium and water is Water is the dispersion medium and oil is the dispersed phase the dispersed phase They are greasy and not water washable They are non greasy and easily removable from the skin surface They are used externally to prevent They are used externally to provide evaporation of moisture from the surface of cooling effect e.g. vanishing cream skin e.g. Cold cream Oil soluble drugs are more quickly released Water soluble drugs are more quickly from w/o emulsions released from o/w emulsions They are preferred for formulations They are preferred for formulations meant.meant for external use like creams for internal use as bitter taste of oils can.be masked W/O emulsions go not give a positive O/W emulsions give a positive conductivity test as oil is the external phase conductivity test as water is the external.which is a poor conductor of electricity phase which is a good conductor of.electricity 01/19/2025 PHT 312 12  EMULSIFYING AGENT:  Definition:  Emulsions are stabilized by adding an emulsifying agent. These agents have both a hydrophilic and a Lipophilic part in their chemical structure.  All emulsifying agents get adsorbed onto the Oil : water interface to provide a protective barrier around the dispersed droplets.  In addition to this protective barrier, emulsifiers stabilize the emulsion by reducing the interfacial tension of the system. CLASSIFICATION OF EMULSIFYING AGENTS:  Emulsifying agents can be classified according to: 1) chemical structure:  Synthetic Emulsifying Agents  Natural Emulsifying Agents  Finely Dispersed Solids  Auxilary Agents 2) Mechanism of action:  Monomolecular  Multi-molecular  Solid particle films. SYNTHETIC EMULSIFYING AGENTS 1) Anionic: (pH > 8)  Sodium stearate  Potassium laurate  Sodium dodecyl sulfate  Sodium sulfosuccinate.  Sodium or potassium oleate  Triethanolamine stearate  sodium lauryl sulfate. 2) Cationic: (pH 3-7)  Benzalkonium chloride,  Benzethonium chloride  Quaternary ammonium salts.  3) NON IONIC (PH 3-10)  Polyglycol,  Fatty acid esters,  Lecithin.  Sorbitan esters (Spans).  Polyoxyethylene derivatives of sorbitan esters (Tweens),  Glyceryl esters. * * * Cationic and Anionic surfactants are generally limited to use in topical, o/w emulsions * * *  NATURAL EMULSIFYING AGENTS Derived from Plants and Animals: Vegetable derivatives:  Acacia  Tragacanth  Agar  Pectin  Carrageenan  Lecithin Animal derivatives:  Gelatin  Lanolin  Cholesterol  FINELY DIVIDED OR FINELY DISPERSED SOLID PARTICLE EMULSIFIERS  These agents form a particulate layer around dispersed particles. Most will swell in the dispersion medium to increase viscosity. Most commonly they support the formation of o/w emulsions, but some may support w/o emulsions. For Instance,,  Bentonite  Veegum,  Hectorite,  Magnesium Hydroxide,  Aluminum Hydroxide  Magnesium Tri silicate.  AUXILIARY EMULSIFYING AGENTS  A variety of fatty acids (e.g., stearic acid), fatty alcohols (e.g., stearyl or cetyl alcohol), and fatty esters (e.g., glyceryl monostearate) serve to stabilize emulsions through their ability to thicken the emulsion..  A system was developed to assist in making systemic decisions about the amounts and types of surfactants needed in stable products. The system is called the HLB (hydrophile-lipophile balance) system and has an arbitrary scale of 1 - 18. HLB numbers are experimentally determined for the different emulsifiers..  Low HLB Indicates ?  Low number of hydrophilic groups on the Molecule thus imparting Lipophilic character:  Spans have low HLB numbers, Because of their oil soluble character, Spans will cause the oil phase to predominate and form an w/o emulsion.  High HLB indicates ?  Emulsifier has a large number of hydrophilic groups on the molecule thus imparting hydrophilic Character.  Tweens have higher HLB numbers, Because of their water soluble character, Tweens will cause the water phase to predominate and form an o/w emulsion.  HLB VALUE & APPLICATION  1~3 Anti-foaming agent.  3~6 W/o emulsifying agents.  7~9 Wetting agents.  8 ~ 18 O/w emulsifying agents.  13 ~15 Detergents.  15 ~18 Solubilizing Agents. HOW TO CALCULATE HLB ????  Combinations of emulsifiers can produce more stable emulsions than using a single emulsifier with the same HLB number. The HLB value of a combination of emulsifiers can be calculated as follows: NUMERICAL 1:  What is the HLB value of a surfactant system composed of 20 g Span 20 (HLB = 8.6) and 5 g Tween 21 (HLB = 13.3)? Water Oil CLASSIFICATION OF EMULSIONS BASED ON MECHANISM OF ACTION: 1) Monomolecular film: To reduce the interfacial tension Oil droplets are surrounded by a coherent monolayer of the surfactant which prevents coalescence. If the emulsifier is ionized, the presence of strong charge may lead to repulsion in droplets and hence increasing stability. Adsorbed at oil/water interface to form emulsiom 2) Multimolecular film or Hydrophillic Colloids 3) Finely divided solid particles: They are adsorbed at the interface between two immiscible liquid phases to form Particulate film. STABILITY OF EMULSION  There are 2 intermolecular forces which affect the stability of dispersed system.  Van der Waals force is an attractive force, which tends to destabilize the emulsion.  Electrostatic force is a repulsive force, which gives stability to the emulsion.  When the total attractive forces > total repulsive forces, the emulsion is unstable.  When total repulsive forces > total attractive forces, the emulsion is stable.  Often, emulsions are inherently unstable.  The small suspended droplets first coalesce into less stable, larger droplets. This coalescence then continues until the emulsion breaks into two layers. STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION STABILITY OF EMULSION IMPORTANCE  :1. Improved bioavailability: Emulsions can enhance the absorption of poorly soluble drugs, increasing their effectiveness.  2. Enhanced solubility: Emulsions can solubilize drugs that are insoluble in water, making them easier to administer.  3. Targeted delivery: Emulsions can be designed to target specific sites in the body, reducing side effects and improving efficacy CONT…… .4. Improved patient compliance: Emulsions can be formulated to have a pleasant taste or texture, making medications more acceptable to patients.  5. Increased stability: Emulsions can protect sensitive drugs from degradation, extending their shelf life.  6. Reduced toxicity: Emulsions can reduce the toxicity of certain drugs by encapsulating them in a protective vehicle.  7. Improved topical delivery: Emulsions can enhance the delivery of topical drugs through the skin, improving localized treatment.  8. Parenteral delivery: Emulsions can be used for injectable drugs, providing a stable and consistent formulation.  9. Ocular delivery: Emulsions can be designed for ocular administration, improving the delivery of drugs to the eyes.  10. Personalized medicine: Emulsions can be tailored to individual patients' needs, providing a more personalized treatment approach. EXAMPLES  1. Mayonnaise: A stable emulsion of oil, egg yolks, vinegar, and water.  2. Milk: A natural emulsion of butterfat globules in water.  3. Cream: A mixture of butterfat globules in water, similar to milk but with a higher fat content.  4. Lotions and creams: Cosmetic emulsions of oil and water, often with added ingredients like fragrances and preservatives.  5. Ice cream: A frozen emulsion of cream, sugar, and flavorings. CONT…….  6. Salad dressings: Emulsions of oil and vinegar  7. Pharmaceuticals: Some medications are emulsions, like creams or ointments for skin application.  8. Food products: Emulsions are used in many food products, such as: - Margarine - Chocolate - Sauces (e.g., soy sauce, teriyaki sauce) - Beverages (e.g., coffee creamers, fruit smoothies)  9. Industrial applications: Emulsions are used in various industrial processes, like: - Paints and coatings - Adhesives - Textile finishing - Paper coatings HERE ARE SOME EXAMPLES OF PHARMACEUTICAL EMULSIONS:1 . Creams:  - Hydrocortisone cream  - Clotrimazole cream -  Mupirocin cream  2. Ointments:  - Petroleum jelly ointment  - Zinc oxide ointment  Bacitracin ointment  3. Lotions:  - Calamine lotion  - Hydrocortisone lotion - . Emulsion injections:  - Liposomal amphotericin B (Fungizone  - Vitamin K injection  5. Topical emulsions: - Acne treatments (e.g., benzoyl peroxide, salicylic acid) - Anti- inflammatory creams (e.g., diclofenac, ketoprofen) - Sunscreens (e.g., oxybenzone, avobenzone)  6. Oral emulsions:  - Vitamin supplements (e.g., vitamin D, omega-3 fatty acids)  - Antacid emulsions (e.g., Gaviscon)  - Protein supplements (e.g., whey protein, casein protein)  7. Eye drops:  - Timolol (Timoptic) THEORIES OF EMULSION MANY THEORIES HAVE BEEN ADVANCED TO ACCOUNT FOR THE WAY OR MEANS BY WHICH THE EMULSION IS STABLIZED BY THE EMULSIFIER. AT THE PRESENT TIME NO THEORY THAT SEEMS TO APPLY UNIVERSALLY TO ALL EMULSIONS. 1- PLASTIC OR INTERFICIAL FILM THEORY 2- SURFACE TENSION THEORY 3- INTERFICIAL TENSION THEORY 4- ELECTRIC DOUBLE LAYER THEORY 5- MONOMOLCULAR THEORY 6- ORIENTED-WEDGE THEORY 7- ORIENTED ADSORPTION THEORY 8- VISCOSITY THEORY THEORIES OF EMULSION PLASTIC OR INTERFICIAL FILM THEORY: * The plastic or interficial film theory places the emulsifying agent at the interface b/w the oil and water, surrounding the droplets of the internal phase as a thin layer of film adsorbed an the surface of drops. * The formation of an o/w or w/o emulsion depends on the degree of stability of the agent in the two phases, with water-soluble agents encouraging o/w emulsions and oil-soluble emulsifer the reverse. THEORIES OF EMULSION SURFACE TENSION THEORY: * According to surface tension theory of emulsification, the emulsifying agents cause a reduction in the interficial tension of the two immiscible liquids, reducing repellent force b/w the liquids and withdrawing the attraction of liquids for their own molecules. * In this way, the surfactants convert large globules into smallones and avoid small globules from coalescing into large ones THEORIES OF EMULSION INTERFACIAL TENSION THEORY: * when two immiscible liquids come in contact, the force causing each liquid to resist breakage is known as interfacial tension. when a high interfacial tension existed b/w two liquids emulsification is difficult, and if the tension could be reduced emulcification facilitated. * the explanation that in oil in water dispersion, the interfacial tension is so great that when two globules of dispersed phase approch each other it withdraw the liquid from b/w them, with the result they coalesce. when the interfacial tension is greatly reduced by the addition of emulsifier the globules remain separate THEORIES OF EMULSION ELECTRIC DOUBLE LAYER THEORY: The oil globules in a pure oil and pure water emulsion carry a negative charge. The water ionizes so that both hydrogen and hydroxyl ions are present. A second layer of oppositely charged ions forms a layer in the liquid out side the layer of negative ions these two layers of oppositely charged ions are known as helmholtz double layer.They are not confined to emulsion but accompany all boundry phenomena. the electric charge is a factor in all emulsions, even those stablized with emusifying agents.