Drug delivery to the skin

Question 1

What are the advantages of skin delivery?

Answer 1

avoids GIT - harsh pH
- skin has higher pH (4-5) - allows greater drug stability

avoids 1st pass metabolism

allows lower drug doses - less S.E

increases patient compliance

allows transdermal and local/topical drug delivery

Question 2

Disadvantages of skin delivery

Answer 2

very hard to formulate and achieve skin delivery as skin is a very effective barrier - controls water loss, heat exchange and is impermeable to microbes and foreign molecules

Question 3

What are the 3 main layers of skin?

Answer 3

dermis

viable epidermis

stratum corneum

Question 4

Describe the the different skin structures?

Answer 4

subcutaneous tissue - structured fatty layer around nearly whole body
- provides protection + source of energy

dermis - matrix of connective tissue
- which contains fibrous protein (80%) + glycosaminoglycan gel (20%)
- contains blood vessels, lymph glands, hair follicles and nerve endings

eccrine sweat glands - found in thighs and feet, secrete watery fluid pH = 4-6.8

apocrine sweat glands - 10x larger than eccrine glands, found in armpits and genital regions, secrete milky fluid - sweat odour

sebaceous glands - found on forehead, face, back, opening into hair follicles, secrete sebum - complex mixture of lipids - moisturise skin surface, pH = 5

basement membrane - 500A thick, connected to epidermis via hemidesmosomes

Question 5

Describe the structure of the viable epidermis?

Answer 5

10um thick, stratified squamous epithelium
contain keratinocytes
- 4 distinct layers that are involved in keratinocyte differentiation

basal layer (stratum basale) - contains actively dividing cells

prickle cell layer (stratum spinosum) - contains more flattened cells with nuclei shrunk, cells interconnect with desmosomes, spaces b/w desmosomes allow passage for oxygen + nutrients

granular cell layer (stratum granulosa) - PP chains of keratin aggregates become insoluble fibrous keratin molecules, cells lose nuclei and other organelles - are flattened and compacted

stratum lucidium - found in palms of hands and soles of feet

stratum corneum (horny layer) - contains dead, flat corneocytes
- contains insoluble bundled keratin (70%) and intracellular lipids (30%)
- lipids organised in multi-laminated sheets - ordered bilayer with rigid structure
- principle barrier for skin penetration

Question 6

Difference b/w transdermal and topical delivery?

Answer 6

transdermal - delivery to the systemic circulation via the skin

topical/dermal - delivery to the skin

Question 7

What are the surface treatments?

Answer 7

sunscreens, antimicrobials, antiseptics

Question 8

What are the local treatments?

Answer 8

corticosteroids, cytotoxic, antihistamines

Question 9

What are the appendage treatments?

Answer 9

antimicrobials, depilatories

Question 10

What are the systemic treatments?

Answer 10

nicotine, hormones