Lecture 14: Advanced transdermal drug delivery Flashcards
What are first generation transdermal patches?
- Transdermal patches in clinical use
What are first generation transdermal patches dependent on?
- LogP
- Dose
- Molecular weight
What is the limitation of first generation transdermal patches?
The barrier function of the intact stratum corneum
What are second generation transdermal patches?
Use skin permeability enhancers for improving delivery of small molecular weight drugs
What are third generation transdermal patches?
Disrupt the stratum corneum barrier eg microneedles
What are the requirements for transdermal drug delivery? (8)
- Increase skin permeability
- Reversibly disrupt stratum corneum structure
- Provide an added driving force for transport into the skin
- Avoid injury to deeper, living tissue
- Non toxic
- Non irritant
- Compatible with drugs and excipients
- Patient acceptability
How does the drug go through the stratum corneum?
- Partition into lipids
- Diffusion
- Partition into viable epidermis
- Diffusion through viable epidermis
- Capillary uptake
What do penetration enhancers act on?
Intracellular lipids of the stratum corneum
Give examples of penetration enhancers?
- Oelic acid
- dimethylsulfoxide
- Water
- Azone
Where does the intradermal influenza vaccine deliver vaccines?
Dermis
What does the intradermal influenza vaccine target?
Epidermal langerhans and dendritic cells
What are the parts of a microneedle? (5)
- Plunger
- Flange
- Finger pads
- Window
- Vaccine
What is the drug ‘human growth hormone’ for?
Growth hormone deficiency
How is human growth hormone delivered?
Thermal ablation
What is the drug ‘parathyroid hormone’ used for?
Osteoporosis
How is parathyroid hormone delivered?
Microneedles
Give an example of an electrically assisted transdermal drug delivery?
Radiofrequency electrical cell ablation
How do electrically assisted transdermal drugs work?
- Generate high frequency alternating current (100-500kHz)
- Transferred to skin via array
- Generate transient holes due to thermal ablation
What is the aim of electrically assisted transdermal drugs?
To deliver charged and not lipophillic drugs such as peptides and protiens
What material is used for microneedle assisted transdermal drugs?
- Metal eg steel, lithium
- Polymers eg PlGA, PLA, PCL
