Emulsion stabilizers which increase the viscosity of the continuous phase may

Emulsion stabilizers which increase the viscosity of

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Emulsion stabilizers, which increase the viscosity of the continuous phase, may be used in o/w emulsions, e.g. tragacanth, sodium alginate and methylcellulose
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Stability of Emulsions (Con’t) c) Storage temperature Extremes of temperature can lead to an emulsion cracking When water freezes it expands, so undue pressure is exerted on dispersed globules and the emulsifying agent film, which may lead to cracking Conversely, an increased temperature decreases the viscosity of the continuous phase An increasing number of collisions between droplets will also occur, leading to increased creaming and cracking
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Stability of Emulsions (Con’t) d) Changes which affect the interfacial film. Microbiological contamination may destroy the emulsifying agent Addition of an emulsifying agent of opposite charge, for instance cationic to anionic
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Dispensing Emulsions 1. All oil-soluble and water-soluble components of the emulsion are separately dissolved in the appropriate phase before mixing 2. Emulsions can be extemporaneously prepared on a small scale using a mortar and pestle 3. Electric mixers can also be used, although incorporation of excess air may be a problem
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Storage and Shelf Life 1. An amber medicine bottle should be used (for liquid dosage form) Plain bottles for internal use, fluted bottle for external use with an airtight child-resistant closure 2. Containers with a wide mouth are useful for very viscous preparations (e.g. cream) 3. Some official preparations will have specific expiry dates 4. Should be stored at room temperature
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Making emulsion Rx 100 mL Liquid Paraffin Oral Emulsion BP 1968. Liquid paraffin 50 mL Vanillin 50 mg Chloroform 0.25 mL Benzoic acid solution (5%) 2 mL Methylcellulose 20 2 g Saccharin sodium 5 mg Water to 100 mL
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Making emulsion (Con’t) 1. Method of preparation Mix the methylcellulose 20 with about six times its weight of boiling water Allow to stand for 30 minutes to hydrate Stir mechanically until the mucilage is homogeneous. Dissolve the saccharin sodium in an appropriate volume of water, add it to the mucilage Dissolve the vanillin in the benzoic acid solution and chloroform Add this mixture to the mucilage and stir for 5 minutes
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Making emulsion (Con’t) Add about 40 ml water to the mucilage, stir, make sure that there is no entrapped air in the mucilage Make the emulsion by mixing together 50 mL of liquid paraffin and the mucilage with constant stirring Transfer the emulsion to a pre-tared amber medicine bottle (100ml), add water until it is 100 ml. Closed with a child-resistant closure Shake well to ensure that the emulsion is thoroughly mixed Polish and label the bottle and give a 5 mL medicine spoon with the medicine
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Making emulsion (Con’t) 2. Shelf life and storage Store in a cool, dry place. a 4-week expiry date is recommended 3. Advice and labelling. “Shake well before use”. The emulsion should not be taken within 30 minutes of meal times and preferably on an empty stomach. The importance of fibre and fluid intake in the diet should be emphasized
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  • Fall '16
  • Dr. George Leung
  • Emulsion

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