Transdermal

Question 1

What are the advantages of parenteral routes?

Answer 1

Improved control 
Rapid onset
Enhanced efficacy
Easy use
Increased compliance
Local/targeted drug delivery
Good fall back route

Question 2

What limits parenteral routes?

Answer 2

Poor/variable blood flow

Question 3

Describe IV delivery

Answer 3

Solutions, suspensions, emulsions, reconstituted solids (sterile)
In aqueous buffers at neutral pH
Drugs must be completely solubilised
NO particles
hypertonic solutions can be used with slow administration

Question 4

Describe IM delivery

Answer 4

Prolonged release of oily and particulate doses
Poorly soluble rugs
Excipients must keep an appropriate viscosity and avoid aggregation
Dissolution affected by solubility in biological fluid at injection site
Higher blood flow = higher absorption

Question 5

Describe SC delivery

Answer 5

Solutions and suspensions
0.5-1.5ml
Drugs need to be water soluble and non-irritant
Can use to administer poorly absorbed and unstable drugs

Question 6

Describe IP delivery

Answer 6

Into cavity/organ
Chemo, Dialysis, Diagnostic imaging
Major route of absorption is the portal circulation with leads to first pass metabolism
Larger, water-soluble drugs are absorbed slower than small lipid-soluble ones

Question 7

What are the three TD penetration routes?

Answer 7

Directly across SC
Through sweat ducts
Via hair follicles and sebaceous glands

Question 8

Which delivery system uses sweat ducts, hair follicles and sebaceous glands?

Answer 8

Iontophoretic

Question 9

How much drug can be delivered transdermally?

Answer 9

5-25 mg

Question 10

What are the cells and Matrix of the stratum corneum made up of?

Answer 10

Cells = keratin rich corneocytes

Matrix - lipid extruded by keratinocytes

Question 11

What are the optimum values for a transdermal patch?

Answer 11

<1000 Daltons
MP <200 degrees
LogP 1-3
No/few polar centres
Half life 6-8 hours
50cm2 max patch size
5-20mg/day usually max feasible dose

Question 12

How can a drug/vehicle be enhanced to improve permeation?

Answer 12

Drug
Pro-drug
Ion pairs/complexes
Chemical potential
Eutectic systems
Liposome/vehicle based
Optimal permeability

Question 13

How can the stratum corneum be manipulated to improve permeation?

Answer 13

Hydration
Lipid fluidisation
Powered electrical devices

Question 14

How can thermodynamic activity be increased?

Answer 14

Evaporation of solvent from the warm surface of the skin

Water absorbed from skin to vehicle and acts as an anti-solvent

Question 15

What are the problems with supersaturated systems?

Answer 15

Inherently unstable

Require incorporation of anti-nucleating agents

Question 16

How is SC modification achieved?

Answer 16

Disruption of intercellular lipid lamellar structure
Interactions with intracellular proteins of the SC
Improvement of partitioning of a drug (co-enhancer/co-solvent)

Question 17

What is the ideal outcome of eutectic systems?

Answer 17

Lower the melting point, the greater the organic solubility
MP below or around skin temp enhances drug solubility
Penetration enhancer as second component to fluidise membranes

Question 18

How does water increase skin penetration?

Answer 18

Alters drug solubility and partitioning

Increases skin hydration, swelling and opening of the SC structure so increased penetration

Question 19

How can Keratin be disrupted?

Answer 19

Decylmethylsulphoxide
Ure
Surfactants

Question 20

How can lipids be fluidised?

Answer 20

DMSO
Alcohols
Fatty acids
Terpenes