Dosage Forms- ALL NOTES Flashcards
What is an emulsion?
-A pseudo-stable dispersion of at least two immiscible liquids one of which is dispersed throughout the other in the form of fine droplets - oil and water stabilised by the presence of an emulsifying agent
What are features of emulsions?
-Cloudy or milky, droplet sizes are polydispersed, kiw concentration of surfactant, thermodynamically unstable but kinetically stable
What are the types of emulsion?
-Normal and reverse emulsion
What is normal emulsion?
-o/w emulsion, oil on inside aqueous on outside
What is reverse emulsion?
-w/o emulsion, oil on outside aqueous on inside
What is a cream ?
-Semi-solid emulsions of two immiscible phases stabilised by emulsifying agent
What are o/w ‘watery’ creams?
-Water is the continuous medium while oil is the dispersed so doesn’t feel oily. Can deposit lipids and are readily diluted and miscible with water
What are w/o ‘oily’ creams ?
-More greasy as oil is in the continuous cream, more moisturising due to oily barrier, not easily washable but more spreadable
What determines the type of cream prepared?
-The type of surfactant
What the difference between the requirements for semi-solid creams and runny emulsions ?
-Semi-solid creams require excess surfactant
How do you tell if an emulsion is o/w or w/o?
-Dye solubility test
-Dilution
-Conductivity
-Fluorescence
How does the dye solubility test work?
-Mix emulsion with a water soluble dye and observe under microscope- if droplets are coloured its w/o if system is coloured the o/w
How does the dilution test for emulsion type work?
-If the emulsion is o/w and diluted with water it will remain stable but if its diluted with oil then the emulsion will break
How does the conductivity test for emulsion type work?
-Electric current passed through electrodes, if passed its o/w if not its w/o
How does the fluorescence test for emulsion type work?
-Based on fluorescence of oils under ultraviolet light under a microscope -if whole fluid fluorescent then w/o if spotty its o/w
What is a micro emulsion?
-droplet size is 0.01-0.1 micrometers in diameter
What does HLB mean?
-Hydrophile-lipophile balance
How do you use HLB?
-Match the HLB of surfactants to the HLB of the oil phase
What does higher HLB mean?
-Hydrophilic surfactants that act as solubilising agents
What does a lower HLB mean?
-Lipophilic surfactants that act as w/o emulsifiers
What HLB makes the most stable emulsion?
-Mix of surfactants with high and low HLB
How is a oral syrup made sugar free while still providing equivalent sweetness viscosity and preservation?
-Artificial sweeteners, non-gycogenetic viscosity modifiers, preservatives
What is an example of artificial sweetener?
-Aspartame
What is an example of a non-glycogenetic viscosity modifier ?
-Methylcellulose, hydroxyethlcellulose
What is an example of a preservative ?
-Sodium benzoate, benzoic acid
What is an elixir ?
-Hydroalcoholic solution for oral use
Why aren’t elixirs used more?
-problem with alcohol content in paediatric formulations and adults who wish to avoid alcohol
What are the typical components of oral elixirs?
-Purified water, alcohol, poll co-solvents, sweetening agents, flavours and colours
What is a linctus?
-Viscous preparations that contain the therapeutic agent dissolved in a vehicle made of a high percentage of sucrose
What are linctuses used for?
-Mainly treatment of cough due to soothing actions on inflamed mucus membranes
What is an oral syrup?
- A highly concentrated, aqueous solution of sugar or sugar substitute
What is a suspension?
-Course dispersion in which insoluble particles generally less than 1 micrometer are dispersed within a liquid medium which is usually aqueous
What should have a proper suspension have?
-Homogenous during dosing, easy to re-suspend , proper viscosity, particles should be small and uniform
What does the r value mean in sedimentation?
-Compares the sedimentation layer volume Vs to total suspension volume Vt
What does h infinity mean?
-Height of sedimented layer
What are types of flocculating agents?
-Electolytes, surfactants, polymers
What do flocculating agents do?
-Prevent caking in a suspension
What are features of flocculated systems?
-Particles are aggregated, fast sedimentation, ‘fluffy sedimentation’ , large sedimentation volume
What are features of a deflocculated system?
-Particles remain as discrete units, slower sedimentation, compact sediment, small sedimentation volume
How can you control flocculation?
-Particle size, use of electrolytes to control electrostatic repulsion, addition of flocculating agents
