IC18 - Pharm Tech 3 Flashcards

1
Q

What is the primary barrier to drug crossing skin via transdermal route?

A

Stratum corneum

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2
Q

Compare and contrast between transdermal and topical delivery?

A
  1. Topical: shallow skin penetration. local delivery
  2. Transdermal: Deep skin penetration, systemic delivery
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3
Q

What are the 5 advantages of transdermal delivery?

A
  1. Controlled release (reservoirs, duration of contact) > Decreased dosing frequency
  2. No GI degradation/irritation
  3. Bypasses hepatic first pass effect
  4. Easy termination of input
  5. Non invasive
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4
Q

List the 7 disadvantages and barriers to transdermal delivery.

A
  1. Variability between people and location of administration on body
  2. Stratum corneum > Slow absorption
  3. Skin irritation (interactions and removal)
  4. Could be removed by the patient
  5. Metabolic enzymes
  6. Blood brain barrier (via systemic delivery)
  7. Systemic side effects
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5
Q

What are the 8 factors that can affect transdermal delivery of drug?

A
  1. Skin condition: age, disease, injury, site
  2. Skin thickness (thickness of diffusion layer)
  3. Hydration of skin (stratum corneum)
  4. Stimulation of the skin
  5. Physicochemical properties of drug
  6. Permeation enhancers
  7. Concentration gradient
  8. Area of contact between formulation and skin
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6
Q

What are the ideal drug characteristics for transdermal products?

A
  1. MW: <500Da
  2. H Bond donors: ≤5
  3. H bond acceptor: ≤10
  4. Log P: 1-3
  5. Unionised
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7
Q

List 2 types of formulation for transdermal system.

A
  1. Topical (gel, creams, ointments)
  2. Transdermal (patches)
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8
Q

What are the common excipients for patches?

A
  1. Preservatives
  2. Solvents/co solvents
  3. Viscosity modified
  4. Permeation enhancers
  5. Adhesives
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9
Q

What are the 4 considerations for drug release in polymer matrices?

A
  1. Diffusion coefficient of drug
  2. Surface area
  3. Concentration
  4. Porosity/tortuosity of polymer matrix - determined by intramolecular interactions (crosslinking, hydrogen bonds)
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10
Q

What is the purpose of sealed packaging of transdermal product?

A
  1. Maintain integrity of adhesive
  2. Maintain integrity of product
  3. Maintain hydration
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11
Q

List two materials used for packaging of transdermal patches.

A
  1. Plastic/polymer lining
  2. Aluminium lining
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12
Q

Briefly explain the design of the patches using the membrane design.

A
  1. Drug dispersed in a separate depot
  2. Rate controlling membrane limits the amount of drug release over time
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13
Q

Briefly explain the design of the patches using the matrix design.

A

Drug incorporated in a polymer matrix, separate to the adhesive layer

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14
Q

Briefly explain the design of the patches using the drug-in-adhesive design.

A

Drug combined with adhesive and released from this matrix

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15
Q

What is the purpose of backing layer in patches?

A

Protection of drug and contents

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16
Q

What is the purpose of a membrane in patches?

A

A polymer matrix whereby its composition/chemistry, thickness and porosity/tortuosity determine release.

17
Q

What is the purpose of a liner in patches?

A

Protects adhesive

18
Q

What are some special considerations for transdermal patch?

A
  1. Release rate of drug from patch
  2. Strength of adhesion
  3. Disposal