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OU Pharmaceutics > Exam 5 Spring 2017 > Flashcards

Exam 5 Spring 2017 Flashcards

1
Q

What dosage forms are the only ones that you can use with controlled drug delivery (CDD)?

A
  • tablets

- capsules

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2
Q

What are the types of controlled drug delivery (CDD)?

A

XL, SR, ER, CR, PA, PL, SA, TR

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3
Q

What are CDD useful for?

A

to treat chronic diseases

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4
Q

What is dose dumping?

A

when the CDD fails and delivers the amount of drug in the tablet all at once

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5
Q

Define CDD

A

drug system that is capable of spatial placement and temporal release of a drug

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6
Q

What does spatial placement pertain to?

A

release of drug in a particular location

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7
Q

What does temporal placement pertain to?

A

time release of the drug

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8
Q

What are the ways in which you can maintain sustained plasma levels of the drug?

A
  • multiple dosing
  • intermittent infusion
  • constant infusion
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9
Q

After how many half lives can we assume that the drug is out of the body?

A
  • four

- some literature use 3.3 because that equals 90%

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10
Q

intermittent infusion

A

drug is given continually but not continuously

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11
Q

multiple dosing

A
  • requires strict adherence
  • cannot tolerate missed doses
  • if doses are missed, plasma levels not sustained and may fall below MEC
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12
Q

What is the assumption for CDD?

A

kinetics of drug release governs drug availability

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13
Q

What are the types of CDD systems?

A
  • osmotically controlled
  • swelling controlled
  • diffusion controlled
  • dissolution controlled
  • ion-exchange resin
  • complex formation
  • magnetically controlled
  • electrically controlled
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14
Q

osmotically controlled system

A
  • has a hole in the tablet
  • polymer is semi-permeable
  • pH independent
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15
Q

With respect to osmotically controlled systems, what does it mean that the polymer is semi-permeable?

A

water and GI fluids can enter tablet but not permeable to substances coming out of tablet

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16
Q

example(s) of osmotic agents

A
  • mannitol

- xylitol

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17
Q

What is osmotically controlled systems dependent on?

A
  • size of hole
  • type of polymer
  • type of osmotic agent / osmotic pressure
  • saturated solubility of drug
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18
Q

Example(s) of semi-permeable membranes used to regulate osmotic permeation of water

A
  • cellulose derivatives
  • polyvinyl chloride
  • polyvinyl alcohol
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19
Q

How does the osmotic agent play a role in osmotically controlled systems?

A
  • osmotic agent creates a high osmotic pressure gradient inside the tablet
  • fluid enters the tablet (osmosis)
  • increase in volume -> drug gets pushed out of hole
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20
Q

swelling controlled system

A
  • polymer and drug tightly packed

- once in GIT, polymer swells to release drug

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21
Q

In a swelling controlled system, what is the release of drug dependent on?

A

rate of water sorption in polymer

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22
Q

Example(s) of polymers used in swelling controlled systems

A
  • poly acrylic acid
  • sodium alginate
  • cellulose derivatives
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23
Q

diffusion controlled system

A

polymer is physical barrier to drug release

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24
Q

In a diffusion controlled system, what is the release of drug dependent on?

A
  • nature of polymer

- thickness of polymer

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25
Q

What are the categories of diffusion controlled systems?

A
  • reservoir

- matrix

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26
Q

describe the reservoir diffusion controlled systems

A
  • drug is coated with water-insoluble polymer
  • water penetrate through polymer to reach drug
  • drug dissolved to produce saturated solution
  • saturated solution diffuses through polymer to outside
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27
Q

If the polymer for reservoir diffusion controlled system is water-insoluble, how does the drug diffuse through it to the outside?

A

osmotic movement through polyemeric mesh (space between macromolecular chains)

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28
Q

For reservoir diffusion controlled systems, how can release of drug remain constant?

A

if concentration of drug in the core remains at saturation

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29
Q

describe the matrix diffusion controlled systems

A
  • aka monolithic

- drug dispersed in polymeric matrix

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30
Q

Polymers for diffusion controlled systems

A
  • reservoir’s polymers are water-INsoluble

- matrix’s can be both

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31
Q

fate of polymers for matrix diffusion controlled systems

A
  • erode with tiem
  • dissolve
  • stay intact as ghost matrix
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32
Q

dissolution controlled system

A

dissolution of drug is the major role in drug release

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33
Q

ion exchange resin system

A

drug is resinated and then formulated in it’s respective dosage form

34
Q

What does it mean for a drug to be resinated?

A
  • cationic / anionic drug passed through ion exchange resin
  • cations replace H atoms
  • anions replace OH atoms
  • drug-resin complex = resinated
35
Q

complex formation systems

A
  • drug complexes which are slowly soluble in GI fluid; pH dependent
  • salts of tannic acid used for this purpose
36
Q

Characteristics of controlled release systems

A
  • not for all drugs
  • not all medical conditions need it
  • dissolution and absorption release of drug should be predictable
  • rate of drug release is controlled
  • rate of drug release = rate of drug elimination
37
Q

Ideal drug candidates for controlled release systems

A
  • Absorption/elimination rate shoud not be too fast or slow
  • Uniformly absorbed form the GI tract
  • Effective dose should be small
  • Possess good margin of safety
  • Used for chronic conditions
38
Q

Limitations of controlled release systems

A
  • Dose dumping
  • Termination of therapy is not easy
  • Variable release of drug
  • Absorption of released drug may not be constant
  • Delayed release = delayed immediate effect of drug
39
Q

What does modified release refer to?

A

drug release based on time, course, or location not offered by conventional dosage forms

40
Q

What are the categories of modified release?

A
  • extended release

- delayed release

41
Q

extended release

A

allows a reduction in dosing frequency

42
Q

delayed release

A

releases drug at a time other than promptly after administration

43
Q

What are repeat action tablets?

A

two layer tablet; one layer is IR and second layer is DR

44
Q

What are targeted release tablets/capsules?

A

directed towards a target location in the GI tract

45
Q

What are the different types of mechanisms of drug degradation?

A
  • hydrolysis
  • oxidation
  • isomerization
  • polymerization
46
Q

What are the functional groups prone to hydrolysis?

A
  • ester
  • amide
  • lactone
  • lactam
  • imide
  • carbamate
47
Q

What is the most common cause of drug degradation?

A

hydrolysis

48
Q

hydrolysis

A

drug molecule + water => breakdown products

49
Q

oxidation

A

gaining electronegative atoms or radicals

50
Q

What functional groups are subject to oxidation?

A
  • phenol
  • aromatic amine
  • aldehyde
  • ether
  • unsaturated aliphatic compound
51
Q

What are examples of drugs that are prone to oxidation?

A
  • morphine
  • epinephrine
  • dopamine
  • steroids
  • vitamins
52
Q

formation of free radicals

A
  • can form in presence of heavy metals, peroxides, or atmospheric oxygen
  • generated radicals form more free radicals
53
Q

What are the factors that affect drug stability?

A
  • temperature
  • pH
  • solvent
  • light
54
Q

affect on drug stability: temperature

A
  • for every 10°C rise in temp, degradation increases 2-3 times
55
Q

affect on drug stability: pH

A
  • specific-acid catalytic reaction goes faster at a low pH and a specific-base catalytic reaction goes faster at a high pH
  • optimal pH is only possible for liquid solution formulations–NOT solid dosage forms
56
Q

examples of drug stability with respect to pH

A
  • thiotepa must be reconstituted with basic solution

- thiamine is stable at pH of 2

57
Q

affect on drug stability: solvent

A
  • increased stability = decreased relative permeability

- can add PEG to stabilize substances prone to solvolysis

58
Q

affect on drug stability: light

A
  • catalyze oxidation reaction -> radicals

- must be stored in amber vials

59
Q

What are common stresses when testing stability?

A
  • temperature
  • humidity
  • light
60
Q

What is the purpose of liposomes with respect to drug delivery?

A
  • increase efficacy
  • reduce dose frequency
  • enhance pt compliance
  • minimizing unexpected effects
  • increased half life
  • prepare drugs that are difficult to administer
61
Q

What are liposomes made up of?

A
  • cholesterol

- phospholipid

62
Q

T/ F A drug maintains its kinetics properties even inside a liposome.

A

False; it’s kinetics will depend on liposome properties

63
Q

What happens with increasing phospholipid carbon?

A
  • increase rigidity

- increasing melting point

64
Q

How do you load drugs into liposomes?

A
  • passive loading

- active loading (remote loading)

65
Q

Passive loading

A

Drug is incorporated while the liposome structure is being formed

66
Q

Active loading

A

Drug is loaded after the empty liposome structure is formed

67
Q

Conditions for active loading: ammonium ion gradient

A

– Internal medium: 250 mM ammonium sulfate

– External medium: sucrose

68
Q

Conditions for active loading: hydrogen ion gradient

A

– Internal pH 4.0 (citrate buffer)

– External pH 7.0 (sodium carbonate buffer)

69
Q

What are characteristics of liposomes to consider?

A
  • lamellarity
  • size
  • charge
  • amount of drug loaded
  • presence / type of surface coating
70
Q

Lamellarity of liposomes

A
  • Multilamellar vesicles (MLVs): more lipid phase available; multi-lipid-layers
  • Unilamellar vesicles (ULVs): more aqueous space; one lipid layer
71
Q

Desirable liposome size

A
  • 80-300 nm

- nanoparticles = <100nm even more desirable

72
Q

How is liposome size reduction achieved?

A
  • high shear homogenization

- pushed through pores of defined size

73
Q

When reducing liposome size, how can you narrow size distribution?

A

multiple cycles of homogenization or extrusion

74
Q

Neutral liposomes increase in size. How can we combat against that?

A

use 5-10% of anionic liposome

75
Q

How is lipid oxidation combated?

A

anti-oxidants esp. vit E

76
Q

How can liposome surface be modified?

A

long polyethylene glycol chain (hydrophilic substance)

77
Q

What is the consequence of PEG-lipid?

A

stability against opsonization and uptake by macrophage

78
Q

How does PEG stabilize liposome?

A

PEG is hydrophilic so the body will think that it’s a solvated particle

79
Q

liposome in cancer therapy

A
  • accumulation in solid tumors
  • reduced toxicity
  • increased efficacy
  • enhanced stability
80
Q

AmBisome®

A
  • amphotericin B liposomes for i.v. infusion
  • lipid bi-layer carries drug
  • unilamellar system
81
Q

Myocet®

A
  • increased size to decrease possibility of uptake by macrophage
  • 3 vial system: doxorubicin, buffer, liposome
82
Q

Doxil®

A
  • doxorubicin liposome

- coated with PEG

OU Pharmaceutics (9 decks)

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