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PHAR 224 > Patches > Flashcards

Patches Flashcards

1
Q

What are the two types of topical dermal systems?

A

Dermal Therapeutic Systems (DTS)

Transdermal Therapeutic Systems (TTS)

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2
Q

What elements must be considered for DTS and TTS?

A

Site of Action (Local & Systematic)

Bio-activity and physiochemical properties of the Drug

Formulation excipients and adhesion

Delivery system

Skin structure

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3
Q

What is the rate-limiting step for drug delivery of patches?

A

Stratum corneum still the rate limiting step

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4
Q

What is percutaneous absorption?

A

Percutaneous absorption = absorption through the skin

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5
Q

Describe the process of patch drug absorption

A

Transdermal reaches circulation

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6
Q

What is the objective for dermal therapeutic systems?

A

To maximize delivery of drugs from formulations into stratum corneum, upper epidermis or dermis, and at the same time minimize further absorption through the skin into the systemic circulation.

Intended for localized effect.

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7
Q

What are some advantages of DTS?

A

More uniform delivery at site of application (sustained delivery)

Longer duration (ability to retain drug in SC longer; Substantivity (resistance to wash-off the active drug during showering, swimming)

Deeper penetration (e.g. local anesthetics, anti-inflammatory agents, analgesics

Reduced side effects (reduces irritation due to lower dose, one of s/e of systems is skin irritation)

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8
Q

What is EMLA?

A

DERMAL THERAPEUTIC SYSTEM

Pain –relief : skin numbing cream –> DISC

EMLA: Mixture of local anesthetics

2.5% lidocaine + 2.5% prilocaine

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9
Q

EMLA DISC Application

A

Peel and stick patch, polymer matrix type (cellulose disc in center contains the active and the adhesive is located peripherally

Mark the time of application - Emla cream must be appliedat least one hour beforethe start of the procedure.

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10
Q

EMLA State of Skin for Applicationand use

A

It is used on normal, unbrokenskinto prevent pain before certain procedures such as inserting a needle for injections or drawing blood.

It is also used before certain vaccinations

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11
Q

What are occlusive dressings?Example and USe?

A

DERMAL THERAPEUTIC SYSTEM

Actiderm (hydrocolloid patch) to enhance the efficacy of topically applied steroid preparations

Flexible hydro active dressing

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12
Q

How do occlusive dressings work? What is the role of occlusive dressings as DTS?

A

air- and water-tight dressing which are generally made with a waxy coating so as to provide a total seal (why called oclusisve)

they are used to enhance the penetration and absorption of topically-applied medications

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13
Q

Antimicrobial Agents as a DTS MOA . Indication?

A

Biopatch : a hydrophilic polyurethane foam/sponge containing a broad spectrum antimicrobial agent (chlorhexidine gluconate)

Indication: Reduce Catheter-Related Blood Stream Infections (CRBSI)

Wound dressings: Band-Aids with antibiotics

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14
Q

Biopatch MOA

A

Wrapped around percutaneous devices to reduce the risk of infection

Absorbs up to 8x its weight of percutaneous fluid, continuously releases the drug and inhibits bacterial growth for 7 days

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15
Q

Duofilm Patch MOA

A

salicylic acid in wart treatment appears to be due to a keratolytic action which results in mechanical removal of stratum corneum cells infected with the papilloma virus

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16
Q

Duofilm C.I.

A

Contraindicated in people with Severe circulatory disorders. Also if skin around the corn is infected, inflamed or broken.

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17
Q

Non-invasive diagnostic patches as DTS Examples

A

Analyte collection patches or Transcutaneous chemical collection devices – TCCDs

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18
Q

MOA of Analyte collection patches or TCCDs

A

Band-Aid like patches containing aqueous media and a binding reservoir to prevent back diffusion of analyte into the skin

When affixed to skin the aqueous vehicle creates a conduit between the skin and the patch for the passive diffusion of sweat and chemicals.

Chemical molecules in the epidermal interstitial fluid migrate by passive diffusion across the stratum corneum into the binding matrix.

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19
Q

Drugs that accumulate in TCCDS

A

Drugs that can accumulate in TCCDs: caffeine, theophylline, cocaine, opiates (heroin, morphine) amphetamines, ethanol

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20
Q

TCCDS Study Findings

A

Several studies described a strong correlation between the cumulative amount of the collected drug and the drug level in the body

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21
Q

What are Non-inasive diagnostic patches or TCCD’s used for?

A

Drug monitoring and compliance

Presence of drug of abuse (from systemic circulation)

Toxic chemicals in the work place

Monitoring the level of medically important endogenous compounds

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22
Q

What are the advantages of non-invasive diagnostic patches?

A

Increased window of detection (larger time period)

Acts as a deterrent to drug abuse

Detects Parent Drug and Drug Metabolites

Variable Removal Date

Quick Application & Removal

No Urine Collections

No Sample Substitution

No Sample Dilution

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23
Q

TCCDS Screen for:

A

Screens for: Marijuana, Cocaine, Opiates, Amphetamine/Methamphetamine, PCP & Ecstasy

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24
Q

CFIS stands for….. WHat is it?

A

Non-invasive diagnostic patches

Cystic Fibrosis Indicator System (CFIS) “Sweat Sticker”

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25
Q

How does Cystic Fibrosis Indicator System (CFIS) “Sweat Sticker” work?

A

High concentration of Na and Cl in the sweat of patients with Cystic Fibrosis –> pathogenetic defect.

A small circular patch, collects sweat and chloride ions as a screening test for cystic fibrosis.

In the patch is a chloride-complexing chemical; it produces a color change when the chloride concentration is above 45mM

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26
Q

CFIS Test type

A

It is a screening test NOT monitoring test (Identifies the presence of the disease not for regular monitoring of the condition).

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27
Q

Describe the DEXCOM continous glucose monitoring system? Limitation?

A

MEASURES glucose in the subcutaneous tissue not the blood

Limitation –> rtCGM systems, except for Dexcoms current G6system, have to be manually calibrated to BG levels approximately 2 times per day

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28
Q

Fresstyle Libre Sensor Use

A

Lancet free glucose monitoring system
Also a continuous glucose monitoring system

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29
Q

What is the difference between freestyle libre and dexcom?

A

Dexcom is real time (rtCGM systems) and Libre is intermittent scanning (iscCGM system)

Dexcom is compatible with insulin pumps and has a buildt in alarm when glucose is at or below 3.1 mmol/L (only alert that cannot be turned off)

30
Q

Goal of Therapeutic Application DTS

A

epidermal and dermal drug absorption

31
Q

Goal of diagnostic Application

A

interfacing with dermis

32
Q

Ideal DTS formulation

A

maximize drug penetration to the dermis BUT minimized systemic absorption

33
Q

Objective of TDS

A

Delivery and maintenance of therapeutic levels of drug in the systemic circulation over a long period of time with the most convenience to the patient

34
Q

Major limitation of TDS

A

The major limitation to transdermal drug delivery (TDD) is the skin itself. Stratum corneum (rate-limiting barrier) PLUS

Metabolically active layers of the skin have biotransformation capacity. However, it is considerably lower than in the gut or liver.

35
Q

Describe the mode of action of TDS

A
36
Q

Advatnages of TDS

A

Avoids gastrointestinal drug absorption difficulties
Is an alternative to oral or parenteral administration
Avoids first-pass hepatic metabolism
Multi-day therapy can be achieved by a single application
Extends the activity of drugs with short half-lives
Easy to terminate the drug effect
Smooth plasma concentration of drugs without significant fluctuations for long periods
Ease of self-administration and improved patient compliance

8

37
Q

Limitations of TDS

A

Unsuitable for drugs which sensitize the skin/sensitivity of skin for excipients (rashes, local irritation, erythema, or contact dermatitis.)
Only potent drugs are suitable candidate for TDSs as small doses can be delivered via this dosage system
Highly dependent on patient factors
Very few drugs can be delivered at a viable rate using this route due to low permeability
Inter and intra-individual variability (regional skin site, skin age, changes in peripheral circulation etc.)

38
Q

Counselling of TDS

A

Prepare skin to remove any dirt, lotions, oils, or powders –> affects adhesion

If you do tear or cut the patch, don’t use it –> unpredictable 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 (REMEMBER drugs in patches are potent)

Don’t use a heating pad on your body where you’re wearing a patch  increase absorption kinetics

ALWAYS MAKE SURE TO REMOVE THE OLD PATCH BEFORE WEARING A NEW ONE  Serious risk of overdosing

Dispose off the old patch after first folding it in half with the sticky sides pressed together  reservoir will still have some drug content

39
Q

What drugs are good candidates for TDS?

A

Drug with high potency (dose requirement of less than 25mg/day)
Low molecular weight
Lipophilic
Short half-life
Low melting point (correlates with good solubility within the reservoir)
High skin permeability
Non-irritating and non-sensitizing to skin
Low oral bioavailability
Low therapeutic index (i.e. requires tight control of plasma levels)

Pretty Little Liars Saved Me, not one teenager perservered

40
Q

Types of TDS

A

Reservoir type

Matrix type

Drug-in-adhesive (DIA) type:
single-layer DIA
multilaminate DIA

Dot-matrix

41
Q

Reservoir Types characteristics

A

Separate Drug compartment: contains drug solution or suspension in a reservoir space

Drug delivery control: Membrane control the kinetic of release = controls the passage of drug and other formulation excipients

42
Q

Formulation of reservoir type drug compartment includes

A

drug dissolved/suspended in a solvent e.g. ethanol
liquid excipients
penetration enhancer

43
Q

Kinetics Reservoir TDS

A

Drug release from reservoir systems normally follow zero-order kinetics (proceed at a constant rate irrespective of concentration)

44
Q

Reservoir Type Diagram

A
45
Q

Reservoir Type Adehesive

A

Location of adhesive layer:

mostly a continuous layer on the membrane (face adhesive)
or in a concentric configuration on the perimeter of the patch

46
Q

DIsadvatnage of Reservoir Type

A

Adhesive and drug or adhesive and excipient interactions/incompatibilities can occur

Vulnerable to burst release
Reasons: rupture of the membrane due to material defect, wear, inadvertent puncture

47
Q

Examples of Resrvoir Type

A

Trans-derm Nitro

Androderm

48
Q

Matrix Type diagram

A
49
Q

Difference between matrix and reservoir

A

Rate controlling is the matrix no rate controlling membrane.

In the reservoir patch, the membrane limits the rate of drug delivery; in the matrix system, it is the formulation of the drug/polymer matrix

50
Q

Matrix Type Drug Compartment

A

Drug compartment
contains drug solution or suspension form in a matrix
Most simple design: a drug containing semisolid disc is held in contact with the skin by an adhesive tape

Drug delivery control - Rate controlling matrix and the stratum corneum (first order)
NO membrane

51
Q

Formulation of matrix type drug compartyment is:

A

drug dissolved/suspended in a semisolid
penetration enhancer

52
Q

Matrix Type Kinetics

A

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

53
Q

Adhesive Matrix Type

A

Matrix can itself act as an adhesive layer.
It can also be a separate layer

54
Q

Diasdvantage Matrix Type

A

The protective overlay maybe mistaken for the part to be applied on the skin (unlikely if patient is properly trained/can also be avoided via clear labeling)

Total patch surface area can be a lot larger than the actual drug delivery surface
(BUT new systems have overcome this limitation by making system sizes equivalent to effective release area of the patches)

55
Q

Examples of Matrix Type

A

Exelon (Alzheimer’s disease)

Sandoz- Fentanyl patch (pain management)

56
Q

Drug in adhesive type diagram

A
57
Q

DIA Drug Compartment

A

Contains the drug dissolved in an adhesive formulation
Represent the ‘state-of-the-art’ in transdermal delivery system design
Extremely comfortable
Patch is very thin
Maximum utilization of surface area of the patch

58
Q

Formulation of Drug Compartment DIA

A

drug dissolved in a pressure sensitive adhesive (PSA)
e.g. PIB (polyisobutylene), silicone or acrylate type
adhesive composition must be customized for each drug

59
Q

Delivery DIA Kinetics

A

Drug delivery control - Rate controlling adhesive and the stratum corneum

First-order kinetics of drug release (release proportional to drug concentration within the adhesive)

60
Q

Locationof Adhesive DIA

A

Location of adhesive layer:
entire surface of the patch – maximum utilization of surface area for drug release

the multi-laminate design can be used where more drug can be released through the membrane in the upper DIA compartment into the lower DIA compartment

61
Q

Diadvantage DIA

A

The first-order release characteristics (when drug concentration in adhesive falls, constant drug delivery profile is difficult to maintain) – to overcome this problem
multi-laminate DIA

62
Q

DIA Examples

A

Estradot (Management of post menopausal symptoms)

EVRA (Birth control patches)

NEUPRO® (rotigotine transdermal system) | Dopamine Agonist

first and only Parkinson’s “patch“

63
Q

Can patche types be interchanged oif same drug?

A

NOT all TDS for same drug will have same mechanism e.g. nitroglycerin patches Transderm Nitro (reservoir) while Nitro-Dur and Mylan-Nitro patch (adhesive type).

64
Q

DOt Matrix Drug Compartment

A

Acrylic: to hold the drug in high concentration
Semisolid suspension; the microscopic drug-in acrylic droplets evenly dispersed in the non-compromised silicone adhesive

65
Q

Formulation of Drug Compartment DOt-Matrixx

A

drug dissolved in acrylic
Adhesive: silicone polymer

66
Q

Dot Matrix Daily Dose

A

Dot-matrix technology (daily dose = 0.025 mg per day)

67
Q

Medication Errors with Patches

A

Confusion factor
–> many different patch designs, dosage strength, frequency of administration, shape, size, color, site of administration (we discussed interchangeability …)

Improper application (Imporant to tell patient to follow package inserts carefully)
peeling not just 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) – so important to tell them to REPLACE the old one. It also increases the risk of overdosing because of the left over medication.
must remove the protective liner
location where the patch should be applied THAT is very critical especially for the hormone patches.
clear patches are difficult to find on the body when its time to remove them (e.g. by caregivers)

Nomenclature issues
mg/h, mg/day, mcg/h, mg/day/week
TTS =Transdermal Therapeutic System (NOT Tuesday, Thursday, Saturday)

Dosing intervals ((dosing regimen to be defined - frequency of application) for example fentanyl patches needs to ne changed EVERY 3 days.
may be daily, every 3 days, twice weekly, weekly, every 3 weeks etc.
the longer the time between patches the greater the risk for forgetting where the old patch is

Pediatric patch issues
cutting patches for a pediatric patient – not possible with reservoir types but maybe done with matrix or DIA types

Safe storage
It may be appealing for young children.

67
Q

Dot Matyrix Example

A

NOven - Daytrana –> methylphenidate

68
Q

Iontrophoresis

A

The main force used to drive substances across the stratum corneum is the electrical driving force, where there is charged particle movement via electrophoresis. This way, a persistent low-voltage current enables the diffusion of substances across the stratum corneum. An electrical current can control drug delivery rate under the control of either a microprocessor or the patient.

69
Q

IONTophoresis Example

A

IONSYS (fentanyl iontophoretic transdermal system)

Fentanyl hydrochloride for pain control
Extended Release
Electrically Controlled and Patient-activated
Used for the treatment of hospitalized patients.
Designed to deliver a 40-mcg dose of fentanyl (equivalent to 44.4 mcg of fentanyl hydrochloride) over a 10-minute period upon each activation of the dose button

PHAR 224 (4 decks)

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