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Biopharmaceutics > Transdermal Drug Delivery > Flashcards

Transdermal Drug Delivery Flashcards

1
Q

What are the types of topical formulations?

A

Ointment, emulsions, creams, and pastes

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2
Q

Topical formulations were originally used for local treatment but can be used for?

A

Systemic

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3
Q

What are the 5 unique characteristics of TDD?

A

Convenience
Acceptance
Versatility
Sophistication (provide precise, long lasting drug delivery)
Drug selectivity
Slow reactivity (can’t be used for emergency purposes)

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4
Q

What are the three major tissue layers in skin?

A

Epidermis, dermis and subcutaneous fat

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5
Q

What are the two sub divisions of the epidermis?

A

Stratum germinativum and stratum corneum

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6
Q

What is the primary barrier to percutaneous drug absorption?

A

Stratum corneum

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7
Q

What skin layer is responsible for the elastic properties?

A

Dermis

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8
Q

What attaches the dermis with its blood vessels to the underlying structure?

A

Subcutaneous tissue (contains fat)

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9
Q

When the skin is warmer, circulation occurs more effectively. What does this also increase?

A

It helps draw chemicals in to the blind circulation efficiently in drugs that have percutaneous penetration abilities

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10
Q

What are some environmental factors affecting transdermal absorption?

A

Age
Race
Gender
Skin health

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11
Q

Is senile skin barrier compromised?

A

False, although dry skin does have less moisture on the surface, reducing drug permeation

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12
Q

Why are occlusive wrappings applied to the skin in some cases?

A

To seal off water loss as humidity increases skin permeability, facilitating drug release.

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13
Q

What can be added to formulations to facilitate drug permeation across the skin?

A

Skin penetration enhancers, which have reversible destructive effects in the skin, which increases permeability.

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14
Q

How is a concentration gradient established across the skin up to the outer reaches of skin microcirculation?

A

The drug diffuses out of its carrier and it partitions either to the stratum corneum or the sebum filled ducts of the hair follicles. From these locations, the drug can diffuse to the viable epidermal and dermal points of entry.

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15
Q

Which layer of the skin, if damaged, allows many chemicals to gain systemic entrance at an alarming rate?

A

Stratum corneum

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16
Q

Describe ointments.

A

Hydrocarbon-based semisolids containing dissolved or suspended drugs

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17
Q

What determines the stiffness of ointments?

A

The extent that the high molecular weight fraction that precipitates out at above room temperature, forming interlocking crystallites

18
Q

What has slowly replaced ointments, due to the greasy and poor medium characteristics of ointments?

A

Emulsion-type creams

19
Q

What are the two generalized types of creams?

A

Water in oil and Oil in water

20
Q

Why are oil in water creams used more frequently than water in oil?

A

They are pleasing in both appearance and feel after application, and can be used for oozing skin wounds

21
Q

This formulation is a semisolid system in which the liquid phase is trapped within a polymeric ,steri of natural or synthetic gum.

A

Gels

22
Q

What can the fluid phase also contain, other than water?

A

Water miscible organic solvents

23
Q

Describe pastes.

A

Ointments that have a higher percentage (>50%) of insoluble particulates

24
Q

What insoluble ingredients are used in the dispersed one to thicken pastes?

A

Starch, zinc oxide, talc and calcium carbonate

25
Q

Name the four Transdermal Drug Delivery Systems.

A

Membrane Permeation Controlled
Matrix Diffusion Controlled
Microreservoir Dissolution Controlled
Reservoir Gradient Controlled

26
Q

In the members be permeation controlled system, where is the drug reservoir located?

A

It is between a drug-impermeable backing laminate and a rate controlling polymeric membrane, which the drug molecules are released through.

27
Q

What are the three types of drug reservoir in the membrane permeation controlled system?

A

Solid polymer matrix (drug and polyisobutylene)
Semisolid suspension (drug and silicone fluid)
Solution (drug and alkyl alcohol)

28
Q

How can the drug release rate of the membrane permeation controlled system be adjusted?

A

The composition of the drug reservoir formulation
The permeability coefficient
The thickness of the rate-controlling membrane

29
Q

Explain the drug reservoir of the matrix diffusion controlled system.

A

It is formed by homogenously dispersing the active ingredient in a hydrophilic or Lipophilic polymer matrix, then Mildred into disks which are mounted onto impermeable plastic backings with adhesive polymer applied to the circumference.

30
Q

How is the drug release rate for the matrix diffusion controlled system controlled?

A

Controlled by the initial loading dose, drug solubility and diffusivity in the matrix
Drug release is proportional to time

31
Q

The Microreservoir dissolution controlled system is considered a hybrid of which two other systems? Describe its formation.

A

The reservoir and the matrix dispersion systems
First, suspend drug solids in aqueous solution in solubilize R and then homogeneously disperse in a lipophilic polymer, forming thousands of microscopic drug reservoirs.

32
Q

How is the drug release rate controlled in the Microreservoir dissolution controlled system?

A

Microreservoir and polymer matrix

Drug partition or diffusivity mechanism, depending on drug solubility ratio in reservoir and matri

33
Q

This system follows a non-zero order drug release by having a varied amount of drug load in each level, forming a concentration gradient along the multilaminate layers

A

Reservoir Gradient Controlled system

34
Q

What is normally used for in vitro drug release assessment?

A

Diffusion cells, with experimental conditions mimicking biological conditions on skin surface.

35
Q

What are used for skin models for in vitro studies?

A

Artificial, synthetic membranes
Excised animal skin samples (mouse and pig)
Human skin samples (surgical procedure, cadaver)

36
Q

What are the optimal models for in vivo bioavailability studies?

A

Human volunteers provide the most accurate information on drug application and outcomes due to the significant variations between animals and humans

37
Q

What are drug plasma levels proportional to?

A

Drug releasing surface in contact with skin

38
Q

What are the 7 reasons allowing transdermal to be the optimal therapeutic choice

A

Avoid risk of IV injections
Avoid metabolism/ absorption variations of oral
Permit continuous drug administration and prolong half lives
Reduce first pass metabolism
Simplified therapeutic regime
Allow rapid termination of medication if necessary.

39
Q

What are the four physical approaches in improving drug absorption?

A

Stripping the stratum corneum
Hydrating the stratum corneum
Iontophoresis (for large molecules, facilitating ionic species transport)
Thermal energy

40
Q

What are the three chemical approaches in improving drug absorption?

A

Synthesis of Lipophilic analogs (can partition more easily into skin components)
Delipidization of the stratum corneum ( make skin surface more hydrophilic, creating higher skin partition/penetration)
Coadministration of skin permeation enhancer(normally surfactants like esters of sat and unsat FA)

41
Q

What are the requirements of a permeation enhancer?

A

Must cause short term, reversible effects and be compatible with the active ingredients. Safety and toxicity must be studied thoroughly.

42
Q

What are the two biochemical approaches in improving drug absorption?

A

Synthesis of bioconvertable prodrugs

Coadministration of skin metabolism inhibitors

Biopharmaceutics (4 decks)

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