Transdermal Drug Delivery

Question 1

What are the types of topical formulations?

Answer 1

Ointment, emulsions, creams, and pastes

Question 2

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

Answer 2

Systemic

Question 3

What are the 5 unique characteristics of TDD?

Answer 3

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

Question 4

What are the three major tissue layers in skin?

Answer 4

Epidermis, dermis and subcutaneous fat

Question 5

What are the two sub divisions of the epidermis?

Answer 5

Stratum germinativum and stratum corneum

Question 6

What is the primary barrier to percutaneous drug absorption?

Answer 6

Stratum corneum

Question 7

What skin layer is responsible for the elastic properties?

Answer 7

Dermis

Question 8

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

Answer 8

Subcutaneous tissue (contains fat)

Question 9

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

Answer 9

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

Question 10

What are some environmental factors affecting transdermal absorption?

Answer 10

Age
Race
Gender
Skin health

Question 11

Is senile skin barrier compromised?

Answer 11

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

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.

Question 15

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

Answer 15

Stratum corneum

Question 16

Describe ointments.

Answer 16

Hydrocarbon-based semisolids containing dissolved or suspended drugs

Question 17

What determines the stiffness of ointments?

Answer 17

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

Question 18

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

Answer 18

Emulsion-type creams

Question 19

What are the two generalized types of creams?

Answer 19

Water in oil and Oil in water

Question 20

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

Answer 20

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

Question 21

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

Answer 21

Gels

Question 22

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

Answer 22

Water miscible organic solvents

Question 23

Describe pastes.

Answer 23

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

Question 24

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

Answer 24

Starch, zinc oxide, talc and calcium carbonate

Question 25

Name the four Transdermal Drug Delivery Systems.

Answer 25

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

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

Explain the drug reservoir of the matrix diffusion controlled system.

Answer 29

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.

Question 30

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

Answer 30

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

Question 31

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

Answer 31

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.

Question 32

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

Answer 32

Microreservoir and polymer matrix | Drug partition or diffusivity mechanism, depending on drug solubility ratio in reservoir and matri

Question 33

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

Answer 33

Reservoir Gradient Controlled system

Question 34

What is normally used for in vitro drug release assessment?

Answer 34

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

Question 35

What are used for skin models for in vitro studies?

Answer 35

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

Question 36

What are the optimal models for in vivo bioavailability studies?

Answer 36

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

Question 37

What are drug plasma levels proportional to?

Answer 37

Drug releasing surface in contact with skin

Question 38

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

Answer 38

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.

Question 39

What are the four physical approaches in improving drug absorption?

Answer 39

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

Question 40

What are the three chemical approaches in improving drug absorption?

Answer 40

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)

Question 41

What are the requirements of a permeation enhancer?

Answer 41

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

Question 42

What are the two biochemical approaches in improving drug absorption?

Answer 42

Synthesis of bioconvertable prodrugs | Coadministration of skin metabolism inhibitors