L38-skin function and dysfunction

list the functions of the skin

• protection- melanin protects from uv

• chemical and microbial defence- microflora competitiveness

• water loss prevention- brick and mortar structure reduces water loss

• thermoregulation - sweating and vasodilation increases heat loss

• sensation- receptors detect touch, pressure, pain

• immune function-cell initiate immune response

• vitamin d storage- presence of UV-B

what are the two ways that drugs act on the skin/ routes of drug delivery

• locally- dermal/topical

• enter systemic circulation- transdermal

briefly describe what transdermal drug delivery is

transdermal drug delivery uses the skin as a transport matrix and requires the therapeutics to infiltrate towards the hydrophilic dermis and then the blood circulation to achieve their subsequent systemic effects

name three benefits of using the skin as a route for drugs

• it avoids the gastrointestinal degradation and bypasses first pass hepatic metabolism

• its useful for patients who cannot take oral drugs

• it improves patient compliance in chronic therapy

describe the brick and mortar model when discussing the stratum corneum

the stratum corneum is the main barrier to drug penetration

brick- corneocytes ( which are differentiated flat keratinocytes filled with keratin )

mortar- lipid matrix ( a mixture of ceramides, cholesterol and free fatty acids )

what are the three main routes for drug to get through the skin

1. trans follicular- through the hair follicle

2. transcellular- through the cells

3. intracellular- between the cells

describe how hydrophobic and hydrophilic drugs can get through the statum corneum

hydrophobic drugs- travel through the ‘mortar’ the lipid aspect of the corneum

hydrophilic drugs- travel through the ‘bricks’ the corneocytes ( but they still have to navigate through the lipid rich layer )

hydrophobic- prefer intracellular

hydrophilic- prefers transcellular

what the effect of damaged or inflamed skin skin on drug absorption

it increases drug absorption

why would topical drug delivery be used ?

they are applied locally for local therapeutic effects for treatments of infections, acne and inflammation

describe systemic absorption with topical formulations

very minimal especially if the skin barrier is intact

provide three examples of topical drugs

• hydrocortisone creams- reduce inflammation

• clotrimazole- treats fungal infections

• calcipotriol- ointment used to treat plaque psoriasis

what are the two types of transdermal drug delivery

• passive delivery- uses natural diffusion through skin, it doesn’t disrupt the SC

• active delivery- uses physical or chemical methods to bypass or disrupt stratum corneum

what is some of the criteria for a drug to be infiltrated into the skin passively

• high pharmacological potency

• small molecular size

• moderate lipophilicity

• low melting point

• non-irritating

• short half life

what are some advantages and disadvantages to passive transdermal drug delivery

what are some types of active transdermal drug delivery methods

what are the different types of micro needling technology

• solid MN- applied to skin → removed→ formulation like cream is applied after ( poke and patch ) it creates the channels for the drug to go though

• coated MN- applied to the skin → the drug is already on the needles so it dissolves through ( coat and patch)

• hollow MN- applies to skin→ then liquid formulation is applied ( poke and patch)

• dissolving MN- apply to the skin→ microneedles will be dissolved onto the skin→ drug also released with it→ when removed produces an empty patch ( poke and release )

describe what eczema is

describe psoriasis

what is usually given to patients with psoriasis

topical corticosteroids and vitamin d analogues

describe burns

describe acne and sebaceous dysfunction

what is usually given to patients with acne

• benzoyl peroxide reduces bacterial loads

• topical retinoids normalise follicular turnover

briefly describe how trans follicular drug delivery works

• the follicles act as reservoirs allowing the gradual drug release into the surrounding skin

• as hairy skin with hair follicles only accounts for 0.1% of the skin surface area it isn’t common method

whata re the advantages and disadvantages for drug delivery across the nail plate for local treatment

advantages- allows treatment of fungal nail infections

avoids systemic side effect, liver toxicity and first pass metabolism

disadvantages-penetration is slow dues to the crosslinked keratin