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Emulsions
Pharmaceutics 2: Module 4
| Question | Answer |
|---|---|
| What is the basic definition of emulsions | Dispersion of globules/drops in a liquid |
| What form do emulsions exist in? | Can be liquids or semisolids |
| Most emulsions need this to stabilize the system | emulsifying agents |
| For what reasons what an emulsion be chosen as a dosage form? | To improve bioavailability, stability, and palatability. |
| How are emulsions made? | -oil and water - emulsifier -imparting energy added |
| Technical definition of emulsion? | A dispersed colloid system consisting of two immiscible liquid phases stabilized by 1 or more suitable agents. |
| What is the interfacial area? | Interfacial area is the total area of contact between the two liquids in emulsions |
| What is a dispersed colloid system? | A system of dispersed/distributed (not dissolved) Size is 1nm to 1 micrometer (um) |
| What is the immiscible liquid phase? | a phase in which a two immiscible liquids are mixed with the addition of energy, but no emulsifier. |
| What eventually happens to a mixture in the immiscible liquid phase? | As it "ages" (as time passes) coalescence occurs. Causing the mixture to slowly separate again into the two liquid phases |
| When an emulsifier is added to these mixtures, what happens? | The emulsifier forms a physical barrier which prevents droplets from coalescing. |
| What is the basic definition of coalescence? | The merging of elements to form one whole mass |
| What are the types of emulsions? | Simple emulsions, multiple emulsions, microemulsions, self emulsifying (or self micro emulsifying) |
| In emulsions, what does internal/discontinuous/disperesed phase mean? | Is it the phase in which the droplets exist in an emulsions |
| In a coarse dispersion, what is the particle size range? | 1-50 um (micrometers) |
| In emulsions, what does external/continuous phase mean? | It is the phase that contains the surrounding liquid, around the dispersed droplets |
| In a o/w emulsion how much water is there? | 45% or higher |
| In a w/o emulsion, how much water is there? | less than 45% |
| In multiple emulsions, what is going on with the phases? | Smaller droplets are contained within the large droplets, contained within the continuous phase -can be called W/O/W emulsion or O/W/O emulsions |
| What are the uses for multiple emulsion systems? | for delayed or sustained release drug delivery systems |
| How large are particles in microemulsions? | 5-100 nm |
| What are micro-emulsions? | An emulsion with VERY finely dispersed (or subdivided) dispersed phase (discontinuous/internal phase) |
| Are microemulsions thermodynamically stable? | Yes |
| Micro emulsions use a higher concentration of _________. | emulsifier (10-30%) |
| What are self-emulsifying drug delivery systems (SEDDS)? | They are a mixture of an oil, |
| What are SEDDS/SMEDDS? | they are self emulsifying mixtures made from premixed oil-surfactant-cosolvent mixtures |
| Which self emulsifying mixture type (SEDDS/SMEDDS) has more oil? | SEDDS |
| Which mixture has a higher proportion of water? | SMEDDS |
| Of the two types of mixtures, SEDDS/SMEDDS, which has a higher proportion of surfactant? | SMEDDS |
| What makes emulsions advantageous in terms of absorption? | It does NOT require dissolution for absorption to occur |
| In terms of solubility, what type of drugs are most likely going to be more effective in an emulsion? | Hydrophobic drugs (poor solubility) |
| For drugs that are more stable in a(n) ______ phase, they have improved stability in an emulsion | Oil phase |
| What are the 5 signs of physical instability in an emulsion? | Creaming, breaking (or cracking) , aggregation (or flocculation, same thing) , coalescence, and phase inversion |
| Large globules of in internal phase can rise to the top or fall to the bottom, True or False? | True |
| Which multiple distinct globules begin to stick together (but still show distinct spherical shapes), this is called _________ | flocculation or aggregation (same thing) |
| When these distinct globules aggregate and float to the top of the emulsion, this is called _____ | creaming |
| When distinct globules mesh together to form one uniform conglomerate at the top of the emulsion, this is called _______ | breaking or cracking |
| When the globules aggregate and form larger, uniform spheres that are evenly dispersed, this is called _______ | coalescence |
| Overtime, if coalescence is allowed to continue, this can result in _________ of the emulsion | Breaking or cracking (when one large, uniform layer comes together, creating a completely separate phase) |
| Emulsions become physically unstable at what temperatures? | It can become unstable at both high OR low temperatures. |
| How do emulsifiers affect the creaming or sedimentation of the dispersed phase? | It lowers the propensity of the dispersed phase for creaming or sedimentation. A lower percentage of the dispersed phase will want to aggregate and cause sedimentation or creaming. |
| What must you do to find the best emulsifier for a given mixture? | Find an emulsifier with a HLB value that is the same (or very close) to the HLB value of the oily phase of a mixture |
| What factor of emulsion prep can help to reduce creaming? | By reducing the average droplet size in an emulsion, you can reduce creaming. |
| What variable within an emulsion affects upward/downward movement of droplets? | Viscosity controls the rate of upward/downward movement of droplets |
| w/o emulsions typically have a HLB range of | 3-6 |
| o/w emulsions typically have a HLB range of | 8-16 |
| the HLB is an important characteristic of an emulsion to consider when using a _______ surfactant | non-ionic surfactant |
| When trying to obtain the desired HLB, the ration of ________ is important in order to create a stable emulsion | the different surfactants |
| For a o/w emulsion, the internal phase must be at or below what percentage? why? | It is restricted to 60% to "ensure stability" |
| For a w/o emulsion, the internal phase must be at or below what percentage? why? | 30-40%, if above this range, this can increase the risk of phase inversion |
| For IV or oral emulsions, what type of emulsion MUST be used? | It has to be an o/w emulsion |
| While o/w emulsions usually have a HLB range of 8-16, what range is preferred? | 9-12 |
| If the HLB of an emulsion prepared is further away from the HLB that is needed, what will happen? | It will cause the phases to separate faster |
| The correct _______ is just as important as choosing an emulsifier with the correct HLB number | chemical class (or type) |
| Colloidal dispersions consist of which two subclasses? | Nano-emulsion and micro-emulsions |
| Nano-emulsions are considered to be thermodynamically _________ | unstable |
| Coarse dispersions in emulsions have a particle size range around | 1-50 um (micrometers) |
| The major classes of particle sizes in emulsions are | colloidal and coarse dispersions |
| If an emulsion has milky white or opaque appearance, it is likely a _______ dispersion | coarse |
| If an emulsion appears transparent or translucent, it is likely a ______ dispersion | colloidal (micro or nano-emulsion) |
| For colloidal dispersion emulsions, what type of rheology will be observed? | Both micro and nano emulsions are Newtonian |
| For an emulsion with coarse dispersion, what type of rheology will be observed? | Coarse dispersions are non-Newtonian |
| Because of their rheology, coarse dispersions will be ________ in texture | semi-solid |
| Because of their rheology, colloidal dispersions will be ________ in texture | fluid |
| Things like lotions, mineral oil, milk, and mayonnaise are common examples of which type of emulsions? | coarse dispersion emulsions |
| When creating an emulsion for a drug delivery system, what type of dispersion is needed? | colloidal dispersions are needed (micro or nano) |
| Out of the two major classes of emulsion dispersions (colloidal or coarse), which one has better solubility, bioavailability, and stability? | Colloidal |
| Another term for coarse dispersions is | macro-emulsions |
| What is the only subclass of emulsion dispersions that are thermodynamically unstable and can spontaneously form? | micro-emulsions |
| Emulsifying agents which form mono-molecular films around particles in emulsions are | surfactants |
| Emulsifying agents which form multi-molecular films around particles (or droplets/globules) are | hydrophilic colloids |
| Emulsifying agents which form a finely subdivided film around particles are called | solid particle emulsifiers |
| The properties of the film formed at the particle surface (interface) can be determined how? | By the nature of the surfactant and polymers |
| gelatin, casein, acacia, tragacanth, cellulose derivatives, and alginates are all examples of which type of emulsifying agent? | hydrophilic colloids |
| Hydrophilic colloid emulsifiers are used in the formulation of ____ emulsions | o/w emulsions |
| Hydrophilic colloid emulsifiers affect viscosity in what way? | They increase the viscosity in the continuous phase |
| Pickering emulsions or surfactant-free emulsions are emulsions that contain | solid particle emulsifiers |
| Solid particle emulsifiers can be used to make which type of emulsions? | BOTH o/w and w/o |
| Bentonite, kaolin, talc, carbon black, magnesium hydroxide, and aluminum hydroxide are all examples of which type of emulsifying agent? | solid particle emulsifiers |
| Surfactant emulsifiers are divided into which subclasses? | Anionic, Cationic, Amphoteric, and Non-ionic |
| When choosing a surfactant as an emulsifier, what are the requirements they must meet | -nontoxic -compatible with drug, excipients, and container -have optimized concentration (about 2% w/w) |
| Emulsifiers ______ interfacial tension | reduce |
| How do emulsion preservatives protect against microbes? | They penetrate membranes of bacteria and viruses and cause lysis of cells |
| What are some uses of anionic surfactants? | Soaps and detergents |
| Anionic surfactants lose their surfactant properties under what conditions? | When in the presence of cationic surfactants or in acidic conditions |
| Anionic surfactants are used in _____. why? | only used in topical applications due to toxicity when ingested or injected |
| Sodium palmitate, sodium cholate, triethanolamine oleate, and sodium lauryl sulfate are all examples of which type of surfactant? | anionic |
| Primary uses for cationic surfactants are | as bactericidal agents (mostly used as a preservative in topical dosage forms) |
| Cationic surfactants are the most ____ and _____ | toxic and irritant |
| Cationic surfactants lose their surfactant properties under what conditions? | high pH (or basic) conditions as well as in the presence of anionic surfactants |
| Cetylpyridnium chloride, cetyltrimethylammonium bromide, and benzalkonium chloride are all examples of | cationic surfactants |
| Which type of surfactant can act as cationic AND anionic? | Amphoteric surfactants |
| How can we predict whether the amphoteric surfactant will behave as anionic or cationic? | It depends on pH. it will act as anionic at high pH and will act as cationic at low pH. |
| What causes incompatibilities for amphoteric surfactants? | Their properties depend on pH to act in their desired manner |
| N-dodecyl alanine, N-alkyl betaines, and lecithin are all examples of | amphoteric surfactants |
| In the presence of electrolytes and large pH changes, which surfactant is the best choice? | non-ionic surfactants |
| Which surfactant type is used for dosage forms meant to be ingested or injected? | non-ionic is the only surfactant that is stable and non-toxic in the body |
Created by:
cdaughtry