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3153 Psychiatry > IC18 Pharm Tech (Transdermal Patch) > Flashcards

IC18 Pharm Tech (Transdermal Patch) Flashcards

1
Q

What is the main barrier for transdermal patch?

A

Stratum Corneum

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2
Q

Describe the primary barrier for transdermal patch.
What is the most common route for drugs to enter the barrier?

A
  1. Stratum Corneum
    a. 10-20 layers of flattened, stratified, keratinized dead cells → protein hydrophobic keratin (waterproof skin)
    b. Primary barrier to drug crossing the skin
    c. Brick and mortar structure → rigid bilayer structure
    d. Corneocytes cells connected via the red parts which the drugs can go around them
    e. Will NOT go through the corneocytes
    f. (Common route) Drugs access primarily via intercellular lipidic domains → lamellar membrane
    i. Lipids, cholesterol, fatty acid, ceramides
    g. (Minor) some access via sweat ducts, hair follicles but low surface area
    h. Our skin is not entirely hydrophobic as some molecules are still hydrophilic, which allow H bonding to occur → thus allowing absorption of moisture through the skin too
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3
Q

What are the differences between topical and transdermal patches?

A

Topical Formulation vs Transdermal Patch

Water-based/oil-based cream, gel, ointment vs
Patch

  • Solution/suspensions in reservoirs
  • Polymer matrix

Shallow skin penetration vs Deep skin penetration

Local delivery vs Systemic delivery (skin → blood → brain)

Cosmetics
Antiseptic
Anti-inflammatories
vs
Nicotine
Pain relief
Hormonal regulation

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4
Q

What are the factors that affect transdermal delivery across the skin?

A

Factors that affect transdermal delivery across the skin:

  1. Skin condition; age, disease, injury, site
  2. Skin thickness (thickness of diffusion layer)
  3. Hydration of skin (stratum corneum)
    a. Natural / manufactured (occlusive: physical/chemical)
    b. Physical: patch can trap moisture (hyperhydration using occlusive layer)
    c. Chemical: moisturizer
    d. E.g. in Singapore skin are more plump –> channels in stratum corneum are wider allowing more drugs to flow through
  4. Stimulation of skin
    a. Phonophoresis/ultrasound (mechanical vibration)
    b. Iontophoresis (electric current)
    c. Heat
  5. Physicochemical properties of drug (lipophilicity, diffusion coefficient)
  6. Permeation enhancers
    a. E.g. small amts of ethanol can mess with the structure of lipids in skin to wiggle, allowing drugs to flow through
    b. Reversible reduction in barrier resistance of stratum corneum without damaging viable cells
  7. Concentration gradient
  8. Area of contact btw formulation and skin
    (special considerations for transdermal patches)
  9. Release rate of drug from patch (reproducible)
    a. Potential for leaching and extraction of drug into backing/other layer
    b. Temperature e.g. don’t sleep on heating mattress / near heater → ↑absorption of drug
    c. Crystallinity of drug over time → depends on temp., is it crystal/amorphous form → can affect melting point thus affect release rate
  10. Strength of adhesion (between layers, influence of sweat, hair etc.)
  11. Disposal → high concentrations
    a. Need to educate on this fold into ½
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5
Q

What are the factors that affect transdermal delivery across the BBB?

A

see IC13

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6
Q

What are the possible excipients used in transdermal patches?

A
  1. Preservatives →↓microbial growth
  2. Solvents / Co-solvents →↑solubility
  3. Viscosity modifiers → Affect flow behaviour, stability, drug release from polymer matrix
  4. Matric Polymer → String that twist and form a matrix that can slow down and facilitate sustain drug release
  5. Permeation Enhancers
  6. Adhesives
  7. Others e.g. sustain release agents, humectant
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7
Q

What are some examples of solvents/cosolvents and viscosity modifiers?

A
  1. Solvents / Co-solvents →↑solubility
    - Ethanol
    - Propylene glycol
  2. Viscosity modifiers → Affect flow behaviour, stability, drug release from polymer matrix
    - CMC, HPMC
    - Hyaluronate sodium
    - Calcium alginate
    - Carbomer
    - Poly(methyl vinyl ether/maleic anhydride)
    - Povidone
    - Hydroxyethyl cellulose
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8
Q

What are some examples of matrix polymers?

A

Matric Polymer –> String that twist and form a matrix that can slow down and facilitate sustain drug release

  • CMC, HPMC
  • Hyaluronate sodium
  • Calcium alginate
  • Ethylene-vinyl acetate copolymer
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9
Q

What are some examples of permeation enhancers?

A

Permeation Enhancers
- Cyclodextrin
- Glyceryl monooleate
- Ethanol (small smts)
- Propylene glycol

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10
Q

What are some examples of adhesives?

A

Adhesives

  • Glyceryl monooleate (bioadhesive)
  • Calcium alginate
  • Carbomer
  • Poly(methyl vinyl ether/maleic anhydride)
  • Povidone
  • Silicone
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11
Q

What is an example of a sustain release agent?

A

Glyceryl monooleate (sustained release agent)

  • Form like a sponge, complex matrix that has a lot of water channels and lipid channels → slow down release of drug that’s loaded within them since the drug have to go through a “maze”
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12
Q

What is an example of a humectant?

A

Hyaluronate sodium (humectant, hydrate skin)

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13
Q

What are some examples of a preservative/antioxidants?

A
  • Ascorbyl palmitate
  • Na metabisulfite
  • DL-alpha-tocopherol (amphipathic vit E)
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14
Q

What excipient can be use to create the backing layer?

A

Polyester (Polymer for protective backing layer, doesn’t allow water to pass through)

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15
Q

What is drug release from polymer matrices dependent on?

A
  1. Diffusion coefficient of drug
  2. Surface area
  3. Concentration
    a. ↑conc. of polymer, ↑crosslinking and tangling → slow down drug release
  4. Porosity/tortuosity of polymer matrix
    a. Determined by intramolecular interactions (crosslinking, H bonds)
    b. String that twist and form a matrix
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16
Q

What is the packaging and storage like for transdermal patches?

A

Packaging and storage:

  1. Patches sealed in individual pouches
    a. Plastic / polymer lining → maintain moisture
    b. Aluminum lining → protect API/excipients from light
  2. Sealed packaging
    a. Maintain integrity of adhesive, product, hydration
    b. Prevent degradation of drug by oxidation/temperature etc.
17
Q

What are the different types of designs of patches?

A

Design of patches:

  1. Membrane
    a. Drug dispersed in separate depot
    b. Drug is dissolved or suspended in solvent in the reservoir
    c. Rate-controlling membrane limits the amt of drug released over time
    d. 4 layers (backing, drug reservoir, rate controlling membrane, adhesive)
  2. Matrix
    a. Drug incorporated in a polymer matrix, separate to the adhesive layer
    b. 3 layers (backing, rate controlling matrix containing drug, adhesive)
  3. Drug-in-adhesives matrix
    a. Drug combined with adhesives and released from this matrix
    b. 2 layers (Backing, drug-in-adhesive matrix)
18
Q

What are the possible layers in a transdermal patch?

A

Layers:
- Backing layer (usually impermeable plastic)
o Protect drug and contents

  • Membrane
    o Polymer matrix
    o Composition/chemistry, thickness and porosity/tortuosity determine release
  • Adhesives
    o Silicone, rubber and adhesives and permeation enhancers
  • Liner
    o Protects adhesive
19
Q

What are the advantages of Transdermal Patches?

A

Advantages:

  1. Controlled release (reservoirs, duration of contact, size of patch)
    a. Decreased dosing frequency
  2. No GI degradation /irritation
  3. Bypasses hepatic first pass effect (similar to parenteral)
  4. Easy termination of input (can peel off)
  5. Non-invasive
  6. Convenient, ease of administration
20
Q

What are the disadvantages of Transdermal Patches? (9)

A

Disadvantages:

  1. Variability between people and location of administration on body
    a. Might have varying thickness of skin (affect dose given)
    b. Not a major disadvantage
  2. Stratum corneum (primary barrier to overcome)
    a. Hydrophobic
    b. Slow absorption
  3. Skin irritation (interactions and removal)
  4. Could be removed by patients (non-compliant)
  5. Metabolic enzymes in skin
  6. BBB (via systemic delivery)
  7. Systemic ADRs
  8. Wear and tear can increase amt going into the skin –> overdose
  9. If not dispose properly, can harm others e.g. children, pet
21
Q

What are the characteristics of an ideal drug for CNS drug delivery?

A

Characteristics of an ideal drug for CNS drug delivery

  1. MW < 450Da
  2. H bond donor <3
  3. H bond acceptor <7
  4. LogP 1-3 (since skin is hydrophobic, but cannot be too hydrophobic as it will cause repulsion/stuck in the more hydrophilic areas underneath it
  5. Unionised
22
Q

Why is only about 50% of the drug released from the patch into the skin?

A
  • ~45% released in 24hrs → remaining in the patch is to maintain the conc. gradient

3153 Psychiatry (10 decks)

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