Patches
Functions of the skin
- designed to keep xenobiotics (chemical foreign substance) and micro-organisms out
of the body
- contains nerve endings to detect touch, pressure, temperature and pain
- sweat lands to eliminate waste and maintain electrolyte balance
- blood supply
- sweat: thermoregulation
What is the stratum corneum?
Outermost layer of epidermis
Top layer of skin
Dead, flattened skin cells surrounded bu lipids
Serves as a barrier to protect from pathogens, chemicals and UV radiation
Paracellular vs transcellular routes
Transcellular:
- hydrophilic drugs
- penetrates the aqueous regions of keratin filaments
Paracellular:
- most drugs and lipid molecules
- stays in lipid bilayers disrupting lipid regions
- pass between the cells
Topical vs transdermal
topical: only local, the top layers of the skin
transdermal: fooling the stratum corneum to allow drugs into the skin
Passive vs active transdermal delivery
Passive:
diffusion of a drug
constant diffusion rate
depends on skin and patch characteristics
Active:
using a method to aid transfer
e.g. physical (microneedles)
or electrically assisted methods (iontophoresis)
Types of passive transdermal patches
Matrix
Reservoir
Drug in adhesive
Advantages of passive transdermal patches
painless
non invasive
controlled blood levels
termination possible by removing patch easily
less inconvenience e.g. IV administration
vomiting/diarrhoea/coma patients unable to take oral medication
avoidance of the GIT-no 1st pass metabolism, food effects, intestinal degradation, etc
increased patient compliance
Functions of the skin
- designed to keep xenobiotics (chemical foreign substance) and micro-organisms out
of the body
- contains nerve endings to detect touch, pressure, temperature and pain
- sweat lands to eliminate waste and maintain electrolyte balance
- blood supply
- sweat: thermoregulation
What is the stratum corneum?
Outermost layer of epidermis
Top layer of skin
Dead, flattened skin cells surrounded bu lipids
Serves as a barrier to protect from pathogens, chemicals and UV radiation
Paracellular vs transcellular routes
Transcellular:
- hydrophilic drugs
- penetrates the aqueous regions of keratin filaments
Paracellular:
- most drugs and lipid molecules
- stays in lipid bilayers disrupting lipid regions
- pass between the cells
Topical vs transdermal
topical: only local, the top layers of the skin
transdermal: fooling the stratum corneum to allow drugs into the skin
Passive vs active transdermal delivery
Passive:
diffusion of a drug
constant diffusion rate
depends on skin and patch characteristics
Active:
using a method to aid transfer
e.g. physical (microneedles)
or electrically assisted methods (iontophoresis)
Types of passive transdermal patches
Matrix
Reservoir
Drug in adhesive
Advantages of passive transdermal patches
painless
non invasive
controlled blood levels
termination possible by removing patch easily
less inconvenience e.g. IV administration
vomiting/diarrhoea/coma patients unable to take oral medication
avoidance of the GIT-no 1st pass metabolism, food effects, intestinal degradation, etc
increased patient compliance
