Transdermal Delivery (2) Flashcards by Denise Jackson

The epidermis and the dermis both sit on the ______ which is a ________ fat layer.

hypodermis; subcutaneous

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______ is the rate limiting step of the skin. Why?

stratum corneum; because it is very compact and hard to permeate

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T/F There IS blood in the epidermis.

FALSE: NO BLOOD

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______ are the major antigen-presenting cells of the skin

langerhan

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______ contains blood vessels

Dermis

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The stratum cornuem is about _____ microns

10 (dry)-20

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Transdermal patch acts in the ______ while ointments, cream act _____

bloodstream (use the skin as a route of administration); on the skin (localized)

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Drugs only need to pass the ____ to the into the blood

epidermis

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What do sebaceous glands secrete?

oil

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What is the purpose of the sebum secreted by the sebaceous glands?

to lubricate the skin surface and maintain the pH around 5

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_____ disrupts the stratum corneum

shaving

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The resistance of the skin includes: (3)

Rsc (stratum corneum: rate limiting)
Re (epidermis)
Rd (dermis)

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Transdermal patches help to maintain….

the amount of drug in the blood

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When does it make sense to make a patch? (4)

moderately lipophilic
short half life
wide therapeutic index
dose is low (potent)

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What mechanism does transdermal patches use? What does that mean?

passive delivery; drug goes in by diffusion

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If a drug is extremely lipophilic? hydrophilic?

lipophilic: it will go into the skin, but not into the blood
hydrophilic: not go into the skin

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What are some benefits of transdermal patch? (5)

absence of first pass metabolism
sustained release effect (drug concentration goest up–> maintained)
non-invasive
ease of self administration
reduced adverse effects/systemic exposure

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The skin is ____ degrees Celsius. (used in Franz diffusion cells)

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FACTORS AFFECTING SKIN ABSORPTION:
Drug concentration/solubility
If you _____ the drug concentration: ____ the amount that will cross the skin

increase; increase

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FACTORS AFFECTING SKIN ABSORPTION:

Partition coefficient?

how drug balance between hydrophilic and lipophilic parts

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What is the desired LogP for Skin absorption?

1-3.5

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If the LogP is negative then?

hydrophilic: not cross the skin

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If the LogP is greater than greater than 3.5?

lipophilic: will cross the skin–> not go into the blood

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FACTORS AFFECTING SKIN ABSORPTION:
Surface Area
When you ____ the surface area, you _____ the strength

increase: increase

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FACTORS AFFECTING SKIN ABSORPTION: | If you ____ the temperature: _____ the amount of drug going into the body

increase: increase

For transdermal patches the ideal saturation is around...

90%

What is the driving force for the delivery of the transdermal patch for increasing concentrations?

thermodynamic activity, which also depends on the vehicle

flux?

amount of drug that crosses the skin in a defined area (ug/sq cm/h)

What is the ideal permeant flux for a transdermal patch?

1 mg/sq cm/day= 10 mg/day

What are the types of transdermal systems? (2)

- reservoir membrane-modulated system | - drug-in-adhesive diffusion controlled system (matrix)

T/F With an adhesive(matrix) patch you remove the backing membrane.

FALSE: you remove the protective liner NOT the backing membrane

Where is the drug in an adhesive match?

inside the adhesive which is revealed after the protective liner is removed

The type of patch used depends on ......

the solubility

Acrylate based Silicone based Polyisobutylene based are examples of what type of transdermal patch

matrix (adhesive) patch

T/F You SHOULD use an acrylate patch for controlled substances

FALSE: should not

In a reservoir patch, the drug is suspended, so how is the release of the drug controlled?

by the membrane

Where is the loading dose found in reservoir patches?

in the adhesive

What is the reason why reservoir patches are used less commonly?

leaking from the patches

What was the first transdermal product?

transderm-scop (used for motion sickness)

T/F Nicotine patches ONLY have nicotine

TRUE

Using ____ with nicotine patches may act like an enhancer

soap

When are oral narcotics okay to be used with duragesic patches?

for breakthrough pain (immediate release)

One should avoid.... when using a patch (2)

- hairy areas | - placing the patch in the same place over and over

T/F One should touch the sticky surface of the patch?

FALSE: drug will start to go in the blood from fingers-->adhesive gets compromised

T/F It is okay to cut a patch

FALSE: DO NOT cut the patch

After a patch has been applied for the desired time, does it have any drug remaining? If yes, how much?

- the drug does have excess drug because that is required to drive the gradient - 10-90% remaining depending on the patch design

What could happen if the drug concentration in a patch is supersaturated?

matrix is unstable--> crystallization will occur over time

If a patch falls off, can it be placed back by putting a tape around it? How about an overlay wrap that is included with some patches?

-No for both the tape and the overlay wrap because the adhesive is compromised

What is the surface area of patches on the market?

5-40 sq cm

What are some enhancement technologies for skin microporation? (4)

- microneedles - thermal ablation - radiofrequency ablation - laser ablation

_____ works for drugs that are charged or neutral. use low electric current to push the drug into the skin(via anode)

iontophoresis

_______ uses high voltage for a short period of time

electroporation

_____ uses ultrasound (tested to enhance the transdermal delivery--> drives molecules into and across skin)

phonophoresis , sonophoresis

_______ is creating microscopic pores in the skin

skin microporation

skin ONLY allows ____ and ____ drugs to come across

small and moderately lipophilic

Why can't proteins pass into or through the skin?

Large molecular weight and hydrophilic

Type of Skin Microneedle: | Needle goes in makes the pores then comes out. Then the patch is applied

SOLID

Type of Skin Microneedle: - Needle has the drug coated on it - Needle goes in, drug is left in the skin and then the needle comes out - No Patch involved - Not a lot of drug ~1mL

COATED

Type of Skin Microneedle: | Drug is the needle and the needle dissolves in the skin? example

DISSOLVING: maltose

- Which of the following is more likely to be easily delivered through microchannels from a patch applied after microporation? - IgG (MW 150,000 Da) - Terbinafine (MW 291.4)

- IgG (MW 150,000 Da) ANSWER | - Terbinafine (MW 291.4): not needed because it is already moderately lipophilic and small

_____ is the defined as the measurement of the quantity of water that passes from inside a body through the epidermal layer (skin) to the surrounding atmosphere

transepidermal water loss

Pores remain open under ____ conditions

occluded

Maltose micro needles treated skin open to the environment?

NO pores (pores close within 15 hours)

Maltose micro needles occluded by plastic film or by any solution

OPEN pores (up to 72 hours)

How can you determine the drug concentration in the skin? (2)

microdialysis (probe) | tape stripping