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Medicine analysis and design > Microencapsulation > Flashcards

Microencapsulation Flashcards

1
Q

what is microencapsulation?

A

it is a method of enclosing drugs in protective/ modified release coatings or membranes

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2
Q

describe the difference between a reservoir and matrix system

A

reservoir has a drug core surrounded by a polymer shell.
whilst the matrix has drug dispersed throughout the polymer

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3
Q

list some uses of microencapsulation

A
  1. dosage forms
  2. mask unpleasant tastes of drugs
  3. protects against oxidation and hydrolysis.
  4. GI tract targeting
  5. can provide modified release
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4
Q

eudragit RL and RS is a degradable polymer. how does it differ from ‘eudragit L & S’?

A

rate of release only. L & S is gastro resistant so that controls location release in gi tract

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5
Q

what are some factors that makes polymers ideal for microencapsulation? (5)

A
  1. biocompatable
  2. biodegradable
  3. easy to produce
  4. relatively cheap
  5. no adverse reactions with drug
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6
Q

explain how microencapsulated particles are manufactured.

A

particles formed when polymers solidify (as solvent is removed).
Faster this is done the greater the amount of drug that can be encapsulated.
However the faster the polymer solidifies the more likely a porous microsphere/incomplete coating will be produced.
This can result in fast, uncontrolled and premature release

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7
Q

explain what phase separation is (coacervation)

A
  • dissolve coating material(polymer) in a solvent
  • add core drug to form dispersion
  • solubility of polymer reduced to deposit coating on the core
  • then hardening process occurs.
    *only used for microcapsules aka reservoir systems. useful for encapsulating hydrophobic/ poorly soluble drugs
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8
Q

how do you reduce the solubility of a polymer?

A
  1. temp control
  2. add a third component (adding a non solvent
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9
Q

explain how emulsion solvent evaporation/extraction works

A
  1. dissolve polymer in organic solvent then drug added to make solution
  2. emulsifies in aqueous continuous phase containing an emulgent/surfactant.
  3. emulsion agitated by stirring and heat to evaporate organic solvent or addition of continuous phase for extraction.
  4. polymer solidifies around drug and microsphere produced.
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10
Q

explain what an oil-in-water emulsion is and why its used

A

organic phase of containing drug and polymer in organic solvent, then place into a separate solution of water and surfactant.

usually used for hydrophobic drugs

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11
Q

why cant you use an oil-in-water emulsion for hydrophilic drugs

A

the drug will partition from oil phase to water phase. therefore, it will no longer be encapsulated.

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12
Q

what emulsion systems can you use for a hydrophilic drug?

A

oil-in-oil emulsion. two oil phases however they are immiscible with each other.

or preferably a water-in-oil-in-water emulsion. it is quicker to perform than o/o. harder to make a more stable emulsion as three phases rather than two.

however it is quicker and cheaper.

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13
Q

list some factors that affect particle size

A
  1. stirring speed
  2. surfactant conc.
  3. polymer and drug concs.
  4. volume of phases
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14
Q

factors affecting drug encapsulations

A
  1. surfactant conc
  2. polymer : drug ratio
  3. volume of phases
  4. drug solubility in each phase
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15
Q

explain what spray drying is

A

1.Drug is dispersed or dissolved in a solution of the coating material.
2.Drug-polymer solution/suspension is fed as atomised droplets into heated chamber.
3. They are rapidly desolvated producing dry microparticles, which are drawn through to the collector.

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16
Q

list some advantages of spray drying

A
  1. fast process
  2. large yield is common
  3. allows use of hydrophilic and hydrophobic polymers & drugs
  4. easier to scale up than
17
Q

some limitations of spray drying

A
  1. pretty expensive
  2. cant use highly heat sensitive materials.
18
Q

(sample q) describe the four step process of degradation of a water insoluble polymer.

A
  1. polymer hydrates when in contact with biological fluids
  2. bonds in polymer break reducing polymer weight
  3. polymer erodes when weight reaches critical point
  4. dissolution of remaining polymer
19
Q

(sample q) explain the difference between surface and bulk degradation of a polymer & why its important in rug release

A

surface degradation only takes away layers, which releases drug over time.

bulk is less consistent/controlled release as drug is released earlier than desired.

important as the rate of degradation can control release of drug and whether its consistent or not

20
Q

(sample q) difference between emulsion solvent evaporation and extraction

A

in evaporation, the organic solvent that the polymer & drug are dissolved in is evaporated off from stirring or heating of emulsion.

in extraction, its due to addition of more continuous phase makes it diffuse out’ve internal phase faster

Medicine analysis and design (20 decks)

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