What are the functions of the skin?
- protection
- apart of immune, nervous and endocrine system
- maintains tempt, electroyltes, fluid balance
- metabolism of lipids, proteins ect
advantages of transdermal delivery
- convenient
- avoid GI tract
- Avoid first pass
- continious drug administration
- can remove quickly
Disadvantages for transdermal
- for slow release only
- depends on drug pK
- skin irritation
- may develop tolerance
difference between intercellular and transcellular delivery
intercellular = drug moves between the cells, easier to achieve, stays in aqueous stage
transcellular = drug moves as cross flies through cells, must have aqueous and lipid layer, harder to achieve
What influences skin penetration
- age
- condition, injury/disease
- anatomical site
- blood flow
- skin metabolism
- species
where dose the most absorption occur
- scrotum
- forehead
- jaw
How to predict drug suitability? MW MP potency partition half life solubility vol dis
<500 <100 potency 1-3 1-9 hr oily <65L
Reservoir systems
how it is made
characteristics
- Blacking film, drug reservoir, release membrane, adhesive, release liner
- slow and constant
Matrix system
how it is made
characteristics
- backing film, matrix later, release liner
2. initial rapid release, then is slows down, thinner type
Azone
- used to increase skin penetration
- binds to ONE ceramide molecule through H bonding
- leaves gaps in pores allowing drug to pass through
N-9015-Ceramide
actually makes the H bonding between ceramide in skin stronger, thus decrease drug penetration
chemical enhancers
- to increase diffusion coefficient
- increase drug solubility
- azone, terepenes (eucalyptus oil), ethanol
2. propylene glycol, ethanol
physical enhancers
- liposomes (carriers)
- ionphorersis
- sonophoresis
- magnetophoresis
- flexible, may squish themselves to fit between cells
- eletrical current with different charge to drug molecules, thus causes eletrorepulsion and eletroosmotic effect - pushing drugs into skin eg fentanyl patch
- ultrasound wave that shakes up structure of stratnun cornea, easier for drug to move into skin
- magenetic energy
How to Microneedles work?
Solid
Coated with drug
dissolable
hollow
