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20 Cards in this Set
- Front
- Back
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Define suspensions.
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Suspensions are two phase systems which contain finely divided drug particles distributed somewhat uniformly throughout a liquid vehicle (solvent)
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What are suspensions commonly used for?
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Oral admin; topical; perenteral (injectable)
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Define emulsions
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An emulsion is a dispersion in which the dispersed phase is composed of small globules of liquid distributed throughout a vehicle in which it is immiscible.
*Dispersed phase = internal phase. *Dispersion medium = external or continuous phase. *Ex. Oil in water: oil is internal phase, water is external or continuous phase *All are thermodynamically unstable. |
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are suemulsions commonly used for?
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oral, topical, parenteral; semi-solid = topical only
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Define gels
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Gels are semisolids systems consisting of dispersions made up of either small inorganic particles or large organic molecules enclosing an interpenetrated liquid
*Colloidal dispersions (1 nm – 0.5 micron) |
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What is the single gel phase?
Examples? |
Organic gel
Synthetic macromolecules - carbomer gels; Natural gums - tragacanth |
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What is the two phase gel?
Examples? |
Inorganic gels
Aluminum hydroxide gels, USP |
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Additional gel info
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May be thixotropic forming semisolids on standing and becoming liquid on agitation or shaking
*Should be labled as shake well before use *Gel is solid, but dispersed medium is liquid |
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Magmas
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*Aqueous suspension of insoluble, inorganic drugs
*Colloidal dispersions *2 Phase systems (thick and viscous and no suspending agent required) *Ex: bentonite magma and Milk of Magnesia *May be thixotropic forming semisolids on standing and becoming liquid on agitation or shaking *Should be labled as shake well before use. |
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Features of a good suspension
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1. Should pour readily and evenly from a container/bottle
2. Particle size should be: 1. as small as possible with a tight distribution 2. Average particle diameter 1- 50 microns (µm) 3. Particles should 1. settle slowly 2. easily resuspended when the container is shaken |
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What is the name of the equation that deals with sedimenation rate?
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Stoke's law equation
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Explain how a structured vehicle slows down teh sedimentation of a suspension
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1. Increased viscosity of the dispersion medium
2. Decreased diameter of the particles 3. Decreased density of the particle |
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What are the 3 methods used to form controlled flocculation to improve suspension properties?
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Method 1 - Use of a structured vehicle
Method 2 - Controlled flocculation Method 3 - Flocculation in structured vehicles |
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Explain how Method 1 (use of a structured vehicle) improves suspension properties.
Be able to recall 2 types of materials used to form this system. |
Use suspending agents: substances that are used in the suspensions to increase viscosity and slow down sedimentation of the dispersed particles
Ex: methylcellulose, sodium methylcellulose, tragacanth, acacia, gelatin, carbomer, colloidal silicon dioxide and Veegum |
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Explain how Method 2 (controlled flocculatoin) improves suspension properties.
Be able to recall 2 types of materials used to form this system. |
Incorporation of flocculating agents maximizes the sedimentation volume by adsorbing on a surface
Ex: Electrolyte; charged surfactant (both iononic and non-ionic); polymer based flocculating agent |
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Explain how Method 3 (flocculation in structured vehicles) improves suspension properties.
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Polymer and flocculating agents are used.
Combination of method 1 and 2. |
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Describe dry gum method of emulsion preparation.
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Dry gum (traditional method):
4:2:1 ratio for making primary emulsion *4 parts oil *2 parts water *1 part emulsifier (acacia) Incorporate oil, water, and emulsifier all at once - vigorous trituration at high speed until a snapping sound is heard = formation of a thick primary emulsion. *Add remainder of water slowly with trituration to make up volume |
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Describe wet gum method of emulsion preparation.
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Wet gum
4:2:1 ratio for making primary emulsion *4 parts oil *2 parts water *1 part gum Emulsifying agent is mixed in water to form mucilage - then oil is slowly incorporated with vigorous trituration at high speed in mortar. *Add remainder of water to form emulsion |
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Differentiate & describe the different types of emulsifying agents and the way they work
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1. Oil in water emulsion (o/w)
2. Water in oil emulsion (w/o) 3. Water-in-oil-in water (w/o)/w 4. Oil-in-water-in-oil (o/w)/o 5. Creams – semi-solid topical preparations. Can be vehicle for drugs 6. Liniments – liquid or semi-solid preparations intended for application to the skin 7. Lotions – liquid preparations intended for application to skin 8. Ointments – used topically for several purposes |
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Describe the different types of emulsion instability
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1. Optimum phase volume ratio is important
2. Coalescence occurs = reversible (can lead to creaming – creaming is irreversible) 3. Seperation of internal phase from external phase is called “breaking” = irreversible 4. Stability of emulsions is temperature dependent |
