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810 > Transdermal Drug Delivery > Flashcards

Transdermal Drug Delivery Flashcards

1
Q

Transdermal Drug Delivery (TDD) Advantages (5)

A
  1. Avoid GI tract problems - food interactions, stomach pH, substitute for oral (N/V)
  2. Avoid risks and inconvenience of parenteral delivery
  3. Identifiable in case of emergency or overdoses
  4. Avoids first-pass metabolism
  5. Improve patient compliance - multiple days treatment from 1 dose

PRESCRIBE FOR LONG TERM THERAPY

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2
Q

TDD Disadvantages (4)

A
  1. Poor route for certain drugs - skin irritants or color
  2. Limited number of drugs can be administered this way - potency (limited range) and physical/chemical properties (lipophilic and size)
  3. Drug effects continue after patch is removed
  4. Difficult/expensive to develop
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3
Q

Skin Features (6)

A
  1. Stratum Corneum
  2. Sweat pores and glands
  3. Epidermis - stratum corneum, squamous cell layer, and basal cell layer
  4. Dermis
  5. Hair shaft and follicle
  6. Fat layer
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4
Q

Skin Layers (4)

A
  1. Surface - emulsified material of sebum, sweat, loose dead cells (thickness and composition vary)
  2. Epidermis - protect from external environment
  3. Dermis - mechanical function
  4. Subcutaneous fat - can be a drug depot
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5
Q

Skin Appendages

A
  • Blood vessels and nerves - from subcutaneous tissue to dermis
  • Sweat glands - ducts rise from dermis through epidermis
  • Sebaceous glands & hair follicles - extend to surface of skin
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6
Q

Dermis

A
  • 2-3 mm thick

- Matrix of tissue woven from collagen (strength & integrity) and elastin (elasticity)

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7
Q

Dermis Blood Supply

A
  • Temperature and body pressure regulation
  • Delivers nutrients
  • Remove metabolic waste products
  • Reacts within 0.2 mm of skin surface - readily absorbs chemicals penetrating skin
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8
Q

Epidermis Cell Types (4)

A
  1. Keratinocytes
  2. Melanocytes
  3. Merkel Cells
  4. Langerhans Cells
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9
Q

Keratinocytes

A
  • 90% of cells
  • Protective sheath that repels pathogens and fluid loss
  • Mitosis renews epidermis and top most layer is sloughed
  • Main barriers to substances moving in and out of body
  • Consists of 10-15 layers of flattened, keratinized cells stacked in highly organized fashion
  • Cells align parallel to skin surface and lateral edges interdigitate with adjacent cells to create highly ordered lamina
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10
Q

Stratum Corneum

A
  • Composition - 50% proteins, 20% lipids, 30% water and water soluble compounds
  • “Brick and Mortar Wall” configuration
  • Protein = mainly keratin
  • Lipids - ceramides, FFA, cholesterol, cholesterol esters
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11
Q

3 Routes of Drug Penetration

A
  1. Intercellular
  2. Transcellular
  3. Transappendageal - via sweat glands or hair follicles

PATCH PLACEMENT HIGHLY AFFECTS ABSORPTION

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12
Q

Skin Permeability Factors (3)

A
  1. Blood flow - Increased BF: Increased Absorption
  2. Disease - psoriasis, essential FA deficiency, atopic dry skin, etc.
  3. Age - thickness of skin remains same but the structural defects leads to wider cell junctions, lipid lamellae degradation, and increased transdermal H2O loss
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13
Q

Drug Penetration

A

-Passive diffusion - requires concentration gradient

Factors affecting absorption:

  • Drug concentration on skin
  • Size of application area and exposure time
  • Physicochemical drug properties (solubility, oil/water partition coefficient, molecular weight
  • Thickness hydration of stratum corneum
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14
Q

TDD Design Objectives (7)

A
  1. Physico-chemical properties to release drug
  2. Occlude skin so drug travels in ONE direction
  3. Adhere well to skin
  4. Adhesive/vehicle/drug should be non-irritating
  5. Consider size, appearance, placement of patch
  6. No bacterial growth beneath occluded skin
  7. Therapeutic advantage over other routes
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15
Q

KNOW FOLLOWING PATCH STRUCTURES

A
  1. Liquid-filled Laminate Structure
  2. Solid-state Laminate Structure
  3. Drug in Adhesive Structure
  4. Foam Adhesive & Polymer Matrix
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16
Q

Proper Use of TDD

A
  • Apply to clean, dry skin
  • Patch in contact with skin
  • Skin should be hairless, NOT shaved
  • Replacing patch - remove old patch, fold in half, and discard
  • New patch - remove from sealed pouch, remove liner, place in different location
  • Wash hands after handling
  • NEVER cut patches, could cut drug
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17
Q

Patch Precautions

A
  • If patch pulls off, replace it, DON’T tape it
  • Never use for immediate relief
  • Patches may have drugs dissolved in alcohol (avoid use in alcoholics)
  • Absorption varies depending on placement, wear at recommended sites and rotate them
  • Condition of skin is important - adhesion, not broken, callused, irritated, hairy, or moisturized (can increase absorption)
18
Q

Transderm-Scop

A
  • 1st transdermal product
  • Contains Scopolamine - placed behind ear to treat motion sickness and delivers 1 mg per 3 days
  • Scopolamine Attributes - potent, requires lowered plasma levels for therapeutic effects, adverse effects are minimized
19
Q

Nitroglycerin

A
  • Potent and short half life
  • Highly susceptible to first-pass metabolism
  • Side effects at high concentrations
  • Patches - prophylactic, delivers drug over 24 hours, reported in mg/h
  • Nitro-Dur, Deponit, Transderm-Nitro, Nitrodisc, Minitran
20
Q

Nicotine

A
  • Small, lipophillic, short half life
  • Available in strengths of 28 mg, 21 mg, 14 mg, and 7 mg
  • Cigarette delivers 1 mg of nicotine, depending on how much they smoke determines which patch they start on
  • No short-term health risks with patch
  • Nightmares and vivid dreams
  • Patch users are 4x more likely to quit
21
Q

Transdermal Clonidine

A
  • treats high blood pressure
  • Potent, low dose, highly lipid soluble, chronic therapy
  • Catapres-TTS - liquid filled laminate patch that delivers drug over 7 days
22
Q

Estrogen

A
  • Hormone replacement therapy
  • Potent, low dose, chronic therapy, first pass metabolism, stability in stomach
  • Climara - 17B estradiol (natural), drug in adhesive and delivered for 1 week
23
Q

Ortho Evra

A
  • Contraceptive, 20 cm^2 patch
  • 3 layers - release liner, medicated adhesive layer, outer polyester protective layer
  • Apply to butt, upper torso, outer/upper arm, lower abdomen ROTATE
  • Bathe and swim as usual but do not oils, creams, or cosmetics on/around patch area
24
Q

Testosterone

A

Androderm

  • Liquid-filled laminate
  • Applied to back, abdomen, upper arm/thigh
  • NOT applied to scrotum

Testoderm

  • Solid-state laminate
  • Apply to scrotal area
  • Shave skin for optimal contact
25
Q

Liposomes

A
  • Spherical vesicle with membranes of phospholipids and cholesterol bilayer
  • Encapsulated liquid solution inside that traps hydrophilic solutes that can’t readily pass through lipids
  • Hydrophobic drugs - dissolves into membrane
  • Lipid bilayer fuses with other bilayers (in skin) to deliver liposome contents
26
Q

Liposome Advantages and Disadvantages

A

Advantages

  • Increases drug incorporation in stratum corneum
  • Permeation enhancement

Disadvantages

  • Aqueous
  • Poor stability
  • Hard to combine with patch technology
27
Q

Transdermal Spray

A

Mechanism - reservoir formation on upper epidermis layer

EX: Acrux

28
Q

Spray Advantages (3)

A
  1. Improved handling compared to semisolids
  2. Improved dosing compared to semisolids
  3. Less irritation potential compared to occlusive systems
29
Q

Spray Disadvantages (3)

A
  1. Limited application areas compared to gels/creams
  2. Impact of showering, bathing, and swimming
  3. Person to person contamination
30
Q

Gels

A

Mechanisms
-Reservoir formation on upper epidermis layer
-Evaporation of solvents typically result in drug super saturation
EX: AndroGel (evaporation)

31
Q

Gel Advantages (3)

A
  1. Enlarged application area
  2. Less irritation potential due to minimal occlusion
  3. Virtually disappears after application
32
Q

Gel Disadvantages (3)

A
  1. Limited control of application area
  2. Risk of contact contamination
  3. Increased environmental risk where excessive drug is washed off
33
Q

Penetration Enhancers

A
  • Chemical agent that reversibly alters strat. corn. permeability
  • Selection of enhancer - efficacy, lack of toxicity, component compatibility

Both increase percutaneous absorption

34
Q

Mechanism of Enhancers (3)

A
  1. Solvent action - directly solubilize tissue (skin components)
  2. Interaction with intercellular lipids - disrupts highly ordered lamellar structure and increases diffusivity through membrane
  3. Interaction with intracellular proteins - increases permeability through corneocytes
35
Q

Thermal Transdermal Delivery

A

Mechanisms
-Increase permeability of stratum corneum
-Increase dermal blood perfusion
EX: CHADD

Preferred application = local anesthetics and pain management

36
Q

Thermal Transdermal Advantages and Disadvantages

A

Advantages

  • Shortening of lag time
  • Increased permeability rates by 2-3x

Disadvantages

  • Electrical heating requires large batteries
  • Chemical heating only lasts a one-day period
37
Q

Heat Provides… (5)

A
  1. Increased solubility for most drugs
  2. Increased permeability
  3. Increased fluid circulation
  4. Vessel Dilation
  5. Increased release rate of drug from local skin tissue to systemic circulation
38
Q

Sonophoresis Mech/Advantages/Disadvantages

A

Mech - Disordering of lipid bilayer (Increase gapping)

Advantages

  • Shortens lag time
  • Transdermal application of peptides, proteins, and other macromolecules become feasible

Disadvantages

  • Limited or no mobility due to systemic size and energy requirements
  • Skin irritation above certain energy levels and durations

Applications = local anesthetics, pain management, and body fluid monitoring

39
Q

Iontophoresis

A
  • Physical method to increase transdermal delivery
  • Electrical current used both locally and systemically to cause reversible changes in morphology/permeability
  • Delivers ionized species and high MW drugs (proteins and peptides)
  • Drug reservoir (+) and return reservoir-saline (-)

EX: E-TRANS

40
Q

Microfabricated Microneedles

A
  • Needles - long enough to penetrate strat. corn. (10-15 um) but doesn’t stimulate nerves
  • Increases permeability and can deliver high MW drugs (proteins and peptides)

epidermal microstructure tech = under development

41
Q

MicroScrub

A
  • Strat. corn. removed by rubbing directly over skin

- Unique design allows for finite limit of cell removal to prevent excess abration

42
Q

Power Injection Systems

A
  • Dry powder particles - diameter = 1-75 um, stable, high doses
  • Released at high velocities to penetrate skin - helium - propellant
  • NO MW LIMITS - used for vaccines, DNA, etc.
  • Generates “fluid needle” that can be calibrated for injection depth

EX: PharmaJet, liquid needle system

810 (22 decks)

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