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Pharm 124 > Transdermal and Dermal Patches > Flashcards

Transdermal and Dermal Patches Flashcards

1
Q

What are the advantages of TD delivery

A
  • Avoids GI side effects of oral drugs
  • Non-invasive alternative to oral or parenteral administration
  • Avoids first-pass metabolism (directly absorbs into systemic)
  • Multi-day therapy can be achieved by a single application (improves patient compliance)
  • Extends the activity of drugs with short half-lives
  • Easy to terminate the drug’s effect
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2
Q

What are the disadvantages of TD delivery

A
  • Unsuitable for drugs that sensitize the skin
  • Only potent drugs can be used
  • Adhesion of the transdermal delivery system to the skin may be variable (affects delivery)
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3
Q

Oral delivery vs TD

A

TD: blood concentration is constant
Oral: not uniform (curves) and requires readmin

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4
Q

What drugs are suitable for TD delivery

A
  • lipophilicity (oil/water partition coefficient 10-1000 ie. log P 1-3)
  • molecular weight <500
  • melting point <200oC
  • pH of saturated aqueous solution 5-9
  • deliverable dose < 10 mg/day
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5
Q

What are requirements for TTS

A
  • Shelf-life up to 2 years
  • Small patch size
  • Convenient dose frequency (eg. 1/day, 1/week)
  • Adequate skin adhesion
  • No residue
  • Reliable and consistent drug delivery in patients
  • No dermal reactions (contact dermatitis, skin sensitization, erythema, maceration, irritation)
  • Cosmetically appealing and easy to use
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6
Q

What are the 3 types of transdermal devices/patch designs

A
  1. reservoir type
  2. matrix type
  3. drug-in-adhesive
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7
Q

TTS components

A
  • Backing film (faces outside after application)
  • rate-controlling membrane (in reservoir patches or multilaminate patches)
  • drug matrix or vehicle
  • pressure sensitive adhesives (PSA)
  • release liners (adhesive layer)
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8
Q

What are properties of reservoir type patches

A

Rate-controlling membrane: Zero-order drug release (release independent of drug concentration within the reservoir)

Drug formulation: Drug completely or partially solubilized

Adhesive: face adhesive or concentric rim

Total size of patch: increased by 30-80% vs. reservoir area

Incompatibilities: Between adhesive and drug or adhesive and excipient

Dose adjustment: cannot cut patch to adjust dose

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9
Q

Does patch size of reservoir patches correspond to different strengths

A

Yes, strength increases with increase in SA

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10
Q

Where are patches applied

A

location varies (ex. transderm behind the ear, estraderm on butt)

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11
Q

What are the 2 types of Matrix type patches

A

Type 1 - adhesive only on perimeter (increases total SA 30-80% but drug does not come in contact with adhesive)
Type 2 - adhesive on total surface

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12
Q

What are the properties of matrix patches

A

Direct contact with skin: No membrane layer; drug absorption is controlled by the matrix (and to some extent the stratum corneum)

Drug formulation: Drug in solution or in suspension

Adhesive: Type 1 or 2

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13
Q

What are the 2 types of Drug-in-adhesive matrix types

A
  • single layer DIA
  • multi-layer DIA (after application, 1st layer of drug C decreases - more drug can be released through the membrane in the upper compartment into the lower compartment)
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14
Q

Properties of DIA patches

A
  • Rate-controlling adhesive matrix and the stratum corneum
  • First-order kinetics of drug release (release proportional to drug concentration within the adhesive)
  • Patch can be cut to adjust dose
  • adhesive on entire surface of the patch
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15
Q

Advantages of DIA patches

A

Extremely comfortable
Patch is very thin
Maximum use of surface area of the patch

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16
Q

Disadvantages of DIA

A

Has first-order release characteristics:
When drug concentration in adhesive falls, constant drug delivery profile is difficult to maintain
(multilaminate design overcomes this problem)

17
Q

What are patch safety issues that occur with improper application

A
  • Peeling not only the protective layer, but also the adhesive overlay
  • Should be applied directly on the skin (a patient had 4 patches stuck on top of each other)
  • Must remove the protective liner
  • Location where the patch should be applied to (e.g., Testoderm – two types)
  • One patch at a time (old patch removed when the new one is applied)
  • Clear patches are difficult to find on the body when it’s time to remove them, e.g., by caregivers
18
Q

What are safety issues of patches

A
  • nomenclature (mg/h, mcg/h, etc.)
  • dosing frequency (every 3 days, weekly, etc. - the longer the time, the more likely to forget where patch is)
  • physicians error
  • pediatric patch issues (cutting patches)
19
Q

What are rules for TTS application

A
  1. Apply on non-hairy areas (may require hair clipping - shaving/epilation not recommended)
  2. Site of application should be dry —> don’t use in sauna or hot, humid place
  3. Remove old patch before applying new patch
  4. Do not apply to areas with cuts or skin damage
  5. Do not apply below the knee or elbow
20
Q

What are dermal therapeutic systems

A

Used for local dermatological conditions

Maximize delivery of drugs from formulations into the stratum corneum, upper epidermis or dermis, while minimizing further absorption through the skin into the systemic circulation

21
Q

What are benefits of DTS

A
  • More uniform delivery — e.g., local anesthetics
  • Longer duration — ability to retain drug in stratum corneum longer; e.g., salicylic acid for warts and calluses
  • Substantivity — resistance to wash off the active ingredient during showering, swimming
  • Deeper penetration — e.g., local anesthetics, anti-inflammatory agents, analgesics – under occlusion
  • Reduced side effects — (reduces irritation because of lower dose)
22
Q

What are examples of DTS

A
  • Treatment of corns, calluses, warts
  • Pain relief
  • Inflammation
  • Occlusive dressings
  • Antimicrobial agents
  • Cosmetic patches
  • Non-invasive diagnostic patches (drug monitoring, cystic fibrosis indicator system)
23
Q

What are the 2 types of EMLA application

A
  1. Cream - apply cream to skin, tegaderm dressing placed over the cream
  2. Disc - matrix type patch

Pharm 124 (4 decks)

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