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PHAR 224 > Patches > Flashcards

Patches Flashcards

1
Q

What is the target for dermal therapeutic systems?

A

Absorption into the skin alone (systemic absorption is not preferred)

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2
Q

What is the target for transdermal therapeutic systems?

A

Absorption into systemic therapeutic systems is preferred

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3
Q

What are some factors that need to be considered before a patch formulation is finalized?

A
  1. Site of Action (local & systemic)
  2. Bio-activity and physiochemical properties of the drug
  3. Formulation excipients and adhesion
  4. Delivery system
  5. Skin structure
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4
Q

What is the objective for dermal therapeutic systems?

A

Maximize delivery of drugs from formulations into stratum corneum, upper epidermis, or dermis, and at the same time minimize further absorption into systemic circulation

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5
Q

What are some advantages of dermal therapeutic systems?

A
  1. More uniform delivery at site of absorption
  2. Longer duration (ability to retain drug in subcutaneous and resistance to washing off)
  3. Deeper penetration (good for anesthetics)
  4. Reduced side effects (but patients can be more reactive to adhesive)
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6
Q

What is the use of EMLA patches?

A

They are patches that contain a mixture of anesthetics (lidocaine and prilocaine)

They deliver numbing to a localized area (used before inserting needles for injections or drawing blood)

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7
Q

What are some contraindications for dermal patches?

A
  1. Patients with severe circulatory disorders
  2. Broken skin (can result in undesired systemic absorption)
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8
Q

What is the use of occlusive dressings?

A

Flexible hydro active dressing

They provide occlusive effects to enhance penetration and absorption of topically applied medications

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9
Q

What is the use of biopatches?

A

They are a hydrophillic polyurethane foam/sponge containing a broad spectrum anti-microbial agent

Used to reduce catheter-related blood stream infections

Absorbs 8x their weight of percutaneous fluid

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10
Q

What are non-invasive diagnostic patches?

A

Also known as analyte collection patches

  1. Can be used to detect drugs like caffeine, theophylline, cocaine, opiates
  2. Can be used to screen some diseases (cystic fibrosis)
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11
Q

How do DEXCOM monitors work?

A

These devices are measuring glucose levels in the subcutaenous as a proxy for blood glucose

DEXCOM is a real time CGM, provide continous measurements to app (good for tracking and alerting patient about hyper/hypoglycemic events)

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12
Q

What is the objective of transdermal systems?

A

Delivery and maintainence of therapeutic levels of drug in the systemic circulation over a long period of time

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13
Q

What are some examples of transdermal patches?

A
  1. Fentanyl patches (pain management)
  2. Nitroglycerin patches
  3. NRT patches
  4. Birth control patches
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14
Q

What is the major limitation to drug absorption with transdermal patches?

A
  1. Stratum corneum is rate-limiting step
  2. Some metabolic acitivity in stratum granulosum
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15
Q

What are some advantages of transdermal delivery?

A
  • Reduced first-pass effects vs. oral dosage forms (extends activity of short half life drugs)
  • Steadier, sustained release (ex. Duragesic releases at a stable rate for 72h)
  • Useful for patients that have difficulties swallowing
  • Easy to terminate drug effect (remove patch to end release of drug)
  • Less fluctuations in dose due to stable release rate
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16
Q

What are some limitations of transdermal patches over oral dosage forms?

A
  • Local irritation or allergic reaction to adhesice of patch
  • High potency drugs only because only small doses can be delivered via transdermal patches
  • More expensive, less accessible
  • Highly dependent on patient factors (inter-intra individual variability)
  • Very few drugs can be delivered at a viable rate using this route due to low permeability
17
Q

How can oral doses be converted into patch dose?

A

ex. Hydromorphone

  • Step 1: Calculate the total hydromorphone amount patient takes in a day

4mg IR x 6 times/day = 24mg/day

6mg Contin x 2 times = 12 mg/day

Total dose = 36mg/day

  • Step 2: Calculate equianalgesic dose of fentanyl patch for replacement

Used table to find 36mg/day = 50mcg/hr fentanyl

18
Q

What should we counsel patients on for best patch use?

A
  • Prepare skn to remove any dirt, lotions, oils, or powders (affects adhesion)
  • Always make sure to remove the old patch before wearing the old patch before wearing a new one (Serious risk of overdosing)
  • If you do tear or cut the patch, don’t use it (unpredicatable drug response)
  • Using the palm of your hand, press down on the patch. The patch should be smooth, with no bumps or folds (loose fitting will affect drug penetration)
  • You may trim the hair if needed but avoid shaving the area of application (increased chances of irritation; broken skin may pre-dispose higher drug exposure)
  • Don’t use a heating pad on your body where you are wearing a patch (increase absorption kinetics)
19
Q

What are some characteristics of drugs that are good candidates for transdermal delivery?

A
  • Drug with high potency (dose requirement of less than 25mg/day)
  • Low molecular weight
  • Lipophillic
  • Short half-life
  • Low melting point (correlated with good solubility within the reservoir)
  • High skin permeability
  • Non-irritating and non-sensitizing to skin
  • Low oral bioavailability
  • Low therapeutic index (tight control of plasma levels)
20
Q

What are some types of transdermal delivery systems (TDS)?

A
  • Reservoir type
  • Matrix type
  • Drug-in-adhesive (DIA) type:
    a. single-layer DIA
    b. multilaminate DIA
  • Dot-matrix
21
Q

What are some characteristics of reservoir type transdermal therpeutic systems (TDS)?

A
  • Separate drug compartment (drug dissolved in solvent, liquid excipients, penetration enhancer) held back by permeable membrane
  • Adhesive is applied on the skin facing face of the membrane
  • Drug release from reservoir systems normally follow zero-order kinetics (proceed at a constant rate irrespective of concentration)
22
Q

What are the disadvantages of reservoir type transdermal therapeutic systems?

A
  • Adhesive and drug or adhesice and excipient interactions
  • Vulnerable to burst release
23
Q

What are some characteristics of matrix-type transdermal therapeutic systems?

A
  • Contains drug solution or suspension form in a matrix
  • Most simple design: a drug containing semi-solid disc is held in contact with the skin by an adhesive (no membrane)
  • Formulation contain:
    a. drug dissolved/suspended in a semisolid
    b. penetration enhancer

A first-order reaction rate depends on the drug concentration of the drug in the matrix and the statum corneum

24
Q

What are some disadvantages of matrix-type transdermal therapeutic systems?

A

The protective overlay maybe mistaken for the side to be applied on the skin patient is properly trained/can also be a lot larger than the actual drug delivery surface

25
Q

What are the two categories of DIA (drug-in-adhesive) transdermal systems?

A
  • Single layer DIA
  • Multilaminate DIA

review 41 for a diagram of the two types of system

26
Q

What are some characteristics of DIA (drug-in-adhesive) as transdermal therapeutic systems?

A
  • The drug is dissolved in the adhesive formulation
  • Represent the most modern transdermal system
  • Extremely comfortable (thin patch)
  • First-order kinetics of drug release (release proportional to drug concentration within the adhesive)
  • Drug release rate is limited by rate controlling adhesive and the stratum corneum
27
Q

What are the disadvantages of DIA (drug-in-adhesive) transdermal therapeutic systems?

A
  • The first-order release characteristics (when drug concentration in adhesive falls, constant drug delivery profile is difficult to maintain)
  • Multi-laminate designs try to address this issue by having multiple layers that release drug into enrich lower layer that is in contact with the skin (maintains drug gradient between vehicle and skin)
28
Q

What are the characteristics of dot-matrix as transdermal therapeutic systems?

A
  • Combination of two polymers (Acyrillic and Semi-solid suspension)
  • Acrylic (holds the drug in high concentration)
  • Semi-solid suspension (the microscopic drug-in acrylic drops evenly dispersed in the non-compromised silicone adhesive)
29
Q

What are some issues with patches in patient care?

A
  • Patch application (possible med errors can occur, patient not removing old patches and adding new ones, site rotation)
  • Confusion factor (many different patch designs, dosage strength, frequency of administration)
  • Nomenclature issues (mg/h, mg/day, mg/day/week)
  • Dosing intervals
  • Pediatric patch issues (cannot cut reservoir type for kids, but other types can)
  • Safe storage
30
Q

What is iontophoresis?

A

The main force used to drive substances across the stratum corneum is the electrical driving force, where ther is charged particle movement via electrophoresis

31
Q

What is an example of an ionotophoresis transdermal system?

A

IONSYS (fentanyl iontophoretic transdermal system)

Designed to deliver a 40mcg dose of fentanyl (over a 10 minute period upon each activation of the dose button)

Extended release (electricallly controlled and patient-activated)

32
Q
A

PHAR 224 (6 decks)

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