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Pharmaceutics 2 - Winter > 4 - Transdermal > Flashcards

4 - Transdermal Flashcards

1
Q

How is px compliance achieved through the transdermal dosage form?

A
  • Application convenience
  • Proven results
  • Product recognition
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2
Q

Do transdermal drug substances only exert pharmacological effects locally?

A

No, can exert locally and systemically depending on what kind of therapeutic regimen is prescribed

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3
Q

___ molecules cannot be delivered through transdermal administration

A

Large

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4
Q

Do drugs undergo first pass metabolism when administered through the percutaneous route?

A

No

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5
Q

What is the onset of drug action for transdermal drugs?

A
  • Very slow

- May have wide variations among different px due to skin conditions and application approaches

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6
Q

When are transdermal dosage forms generally used and when can they NOT be used?

A
  • Generally used for concentration maintenance and management in long-term therapies
  • Can’t be used for emergency situations
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7
Q

What is advantageous about skin as a dosage route?

A
  • Accessible
  • Large surface area
  • Tolerance to variety of substances
  • Convenience
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8
Q

What makes topical preparations appealing to px?

A
  • Wide choice of products
  • Minimal systemic absorption
  • Individualized amount/method
  • Direct site application
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9
Q

What are characteristics of ointments?

A
  • Long contact time
  • Used on dry sites
  • Greasy
  • Poor drug medium
  • Contain dissolved or suspended drug components
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10
Q

Why can’t ointments be used on moist sites?

A

Greasy and lipophilic components are water-insoluble/immiscible

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11
Q

Why has the use of ointments gradually decreased?

A
  • Can stain clothing

- Difficult to clean after application

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12
Q

What are characteristics of creams/lotions?

A
  • Good drug medium
  • Large drug loading capability
  • Rinsable
  • Can be applied to both dry and wet sites
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13
Q

What are the 2 types of lotions/creams available? Why is used more often and why?

A
  • Water-in-oil (W/O)
  • Oil-in-water (O/W)
  • O/W used more often b/c non-greasy, rinsable, and good for most topical skin purposes
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14
Q

What are some characteristics of gels?

A
  • Lubricating
  • Large drug loading capability
  • Washable
  • Transparent
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15
Q

What are some characteristics of pastes?

A
  • Provide protective barrier
  • Moisture absorption
  • Wet sites
  • Non-greasy
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16
Q

Pastes are basically ointments with ____

A

A high percentage of insoluble particulate solid

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17
Q

Why do pastes make a good protective barrier?

A
  • Form unbroken film
  • Absorb moisture
  • Neutralize noxious chemicals
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18
Q

Are pastes or ointments less greasy? Why?

A

Pastes b/c adsorb fluid hydrocarbon fraction to particulates

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19
Q

What are common oil base excipients used in transdermal products?

A
  • Wax
  • Petrolatum
  • PEGs
  • Stearyl alcohol
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20
Q

What are common aqueous base excipients used in transdermal products?

A
  • Water

- Polymers

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21
Q

What are common viscosity-adjusting excipients used in transdermal products?

A
  • Propylene glycol
  • Glycerin
  • PEGs
  • Polymers
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22
Q

What are common emulsifying excipients used in transdermal products?

A

Surfactants (O/W or W/O)

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23
Q

Do transdermal products generally contain preservatives?

A

Yes

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24
Q

What are the basic steps of manufacturing a transdermal product?

A
  • Heating
  • Mixing
  • Incorporating some medication(s)
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25
Q

What is tested for quality control of transdermal products?

A
  • Drug content
  • pH
  • Alcohol content
  • Viscosity
  • Preservation
  • Minimum fill
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26
Q

Patch has ___% more/less absorption than a tablet. What does this cause?

A
  • 60% more

- Greater chance of adverse effects

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27
Q

What are some ways that the transdermal dosage form improves drug absorption?

A
  • Providers uniform and predictable plasma concentrations
  • No first-pass metabolism
  • Improved bioavailability
  • Prolonged drug effect and duration
  • Reduced administration frequency and adverse effects
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28
Q

Which transdermal products produce local effects?

A
  • Cosmetics
  • Consumer-care products (ex: sunscreen, muscle relaxing cream)
  • Certain medications
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29
Q

Which transdermal products produce systemic effects?

A

Most patches

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30
Q

What is the general structure of skin?

A
  • Epidermis (stratum corneum and stratum germinativum)
  • Dermis
  • Subcutaneous fat tissue
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31
Q

What is the function of skin?

A
  • Retain body fluids/tissues
  • Prevent foreign invasions
  • Feel external senses (heat, cold, pain, pressure)
  • Absorb external attacks
  • Regulate body temp and BP
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32
Q

Which portion of skin controls the rate of drug penetration and absorption?

A

Stratum corneum

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33
Q

What kind of cells are found in the stratum corneum?

A
  • Inactive

- Compacted, dehydrated, keratinized, and replenished

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34
Q

What is found in the dermis?

A
  • Living cells
  • Blood vessels
  • Nerve sensors
  • Lymphatics
35
Q

What are the functions of the subcutaneous fat tissue?

A
  • Temp control
  • Shock absorber
  • Other protection
  • Store energy
36
Q

What is found in the skin appendages?

A
  • Hair follicles

- Various glands

37
Q

What is the function of skin appendages?

A

Metabolism

38
Q

Does drug absorption change based on the area of skin?

A

Yes

39
Q

Should transdermal patches be applied to palms or soles?

A

No, skin is very thick so minimal absorption will occur

40
Q

What are some factors that affect drug absorption of a transdermal product?

A
  • Application site
  • Skin humidity
  • Environment conditions
  • Skin health
  • Drug properties
  • Formulation properties
  • Other (age, gender, race)
41
Q

Dry skin can ____ drug permeation through the skin

A

Reduce

42
Q

What can be done to improve drug absorption on dry skin?

A

Use occlusive wrappings to minimize water loss

43
Q

Broken skin allows for ____ permeability

A

Increased

44
Q

Irritation and mild trauma to skin ___ permeability

A

Increases

45
Q

Does permeability of skin differ btwn genders?

A

No

46
Q

How does race affect drug absorption through the transdermal route?

A

Black skin has more cell layers and is denser than white skin, thus showing less permeability

47
Q

What is the relationship btwn permeation rate and diffusivity?

A

Direct relationship (low permeation rate = low diffusivity)

48
Q

Which sites of the body have low permeation rates?

A
  • Back
  • Forearm
  • Abdomen
  • Back of hand
49
Q

What are the normal sites to apply a transdermal product? Why?

A
  • Arms, chest, thighs

- Easy access, less hair, high tolerance, and invisibility

50
Q

How does humidity increase penetration and absorption?

A
  • Pulls drug out of preparation
  • Increases contact w/ stratum corneum
  • Solubilizes drug and stratum corneum
51
Q

Why does high temp increase penetration and absorption?

A
  • Increases drug diffusivity
  • Increases blood circulation
  • Increases skin hydration
52
Q

What effect does damaged skin have on the PK of a transdermal product?

A
  • More secretion
  • More circulation
  • More metabolism
  • High permeability
53
Q

For transdermal products, are lipophilic or hydrophilic drugs preferred? Why?

A
  • Lipophilic

- Can partition more easily into skin components, most of which are lipophilic

54
Q

For transdermal products, are small or large molecules preferred?

A

Small

55
Q

What is the recommend dose of a transdermal product?

A
  • Less than 20 mg/day

- Dosing once daily or weekly

56
Q

What is the recommend half life of a transdermal product?

A

Less than 10 hours

57
Q

What is the recommend molecular weight of a transdermal product?

A

Less than 400

58
Q

What is the recommend therapeutic index of a transdermal product?

A

Low

59
Q

What occurs in a permeation transdermal drug delivery system?

A

Drug reservoir sandiwched btwn drug-impermeable backing and rate-controlling polymeric membrane

60
Q

What can the drug reservoir be in a permeation transdermal drug delivery system?

A
  • Solid polymer matrix
  • Semisolid suspension
  • Solution
61
Q

What can the rate-controlling membrane by in a permeation transdermal drug delivery system?

A
  • Microporous

- Non-porous polymer w/ specific drug permeability

62
Q

How can drug release rate be controlled w/ a permeation transdermal drug delivery system?

A
  • Varying composition of drug reservoir formulation
  • Varying permeability coefficient
  • Varying thickness of rate-controlling membrane
63
Q

What occurs in a diffusion transdermal drug delivery system?

A
  • Active ingredient homogeneously dispersed in hydrophilic or lipophilic polymer matrix
  • Medicated polymer is molded into a disk, which is then applied to a patch
64
Q

How can drug release rate be controlled w/ a diffusion transdermal drug delivery system?

A
  • Initial drug loading dose

- Drug solubility and diffusivity in matrix

65
Q

In a diffusion transdermal drug delivery system, what is the drug release amount proportional to?

A

Square root of time

66
Q

A dispersion transdermal drug delivery system is considered a hybrid of _____ and _____

A

Permeation and diffusion dispersion systems

67
Q

What occurs in a dissolution transdermal drug delivery system?

A
  • Drug reservoir is formed by suspending drug solids in aqueous solution of water-miscible solubilizer
  • Suspension then homogeneously dispersed in lipophilic polymer
68
Q

How can drug release rate be controlled w/ a dissolution transdermal drug delivery system?

A
  • Drug solubility in microreservoirs and polymer matrix

- Drug partition and diffusivity in polymer matrix

69
Q

In a gradient transdermal drug delivery system, drug release follows ___ order kinetics

A

Zero

70
Q

What is the recommended shelf life for transdermal products?

A

Up to 2 years

71
Q

What is tested in in vitro evaluation of transdermal products?

A
  • Drug release from preparations
  • Drug penetration across skin
  • Simulation of in vivo conditions
  • Diffusion cells and membranes
72
Q

What is tested in in vivo evaluation of transdermal products?

A
  • Drug concentration in blood

- PK/PD parameters

73
Q

What are the objectives of a transdermal drug delivery system?

A
  • Avoid IV administration
  • Bypass oral variations in drug absorption and metabolism
  • Achieve prolonged drug effects
  • Reduce first-pass metabolism
  • Increase overall bioavailability
  • Program drug release rate
  • Improve px compliance
74
Q

What can be physically done to optimize transdermal drug delivery?

A
  • Skin stripping (strip stratum corneum)
  • Skin hydration
  • Iontophoresis
  • Skin heating
75
Q

What can be done chemically to optimize transdermal drug delivery?

A
  • Lipophilic analogs
  • Skin delipidization
  • Skin penetration enhancers
76
Q

What can be done biochemically to optimize transdermal drug delivery?

A
  • Prodrugs

- Skin metabolism inhibitors

77
Q

What do skin metabolism inhibitors do?

A

Increase amount of drug reaching deeper sites or systemic circulation

78
Q

What is iontophoresis?

A

Facilitates transport of ionic species through skin layers by applying a physiological acceptable electrical current

79
Q

What is iontophoresis especially beneficial for?

A

Protein and peptide drug candidates

80
Q

What is electroporation? Does it work on skin membranes or on the drug?

A
  • Application of electric field to living cells to form transient pores for increased permeability
  • Works on skin membranes
81
Q

What is sonophoresis? Does it work on skin membranes or on the drug?

A
  • Use of ultrasound to enhance drug permeation across skin

- Works on skin membranes

82
Q

What are the mechanisms used to enhance permeation?

A
  • Increase solubility in stratum corneum
  • Reduce diffusion barrier of stratum corneum
  • Facilitate drug partition into skin
  • Amplify drug transport through appendages
  • Promote drug partition at stratum corneum
83
Q

What are advantages to prodrugs?

A
  • Improve penetration

- Minimize metabolism

84
Q

What are microneedles used for?

A

Delivering proteins and peptides

Pharmaceutics 2 - Winter (4 decks)

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