Intro to Derm and Derm Pharmacology + Prescribing Flashcards
What is the structure of normal skin?
- Subcutis: fat
- Dermis: collagen + elastin matrix w mucopolysaccharide gel -> immune cells (fibroblasts, dermal dendritic cells, macrophages) -> atrophies as you get older - skin gets more fragile
- Epidermis: outer layer -> keratinocytes (majority), langerhans cells, melanocytes
What are the 3 stages of the hair growth cycle?
- Anagen: active growing phase -> 80-90% of hair
- Catagen: transition phase
- Telogen: resting phase -> roughly 10% of hairs -> hair sheds (nb. pregnancy)
What is the function of normal skin?
- Thermoregulation
- Skin immune system
- Barrier
- Sensation
- Vitamin D synthesis
(7-dehydrocholesterol -> cholecalciferol (vit D3)) - Interpersonal communication (ie. physical appearance, smell, self-identity)
What can sk
- 5 D’s*
- Disfigurement
- Discomfort
- Disability
- Depression
- Death
What are the external causes of skin disease?
- Temperature
- UV
- > photosensitivity (ie. due to meds (NSAIDs, abx, HT meds)
- Chemical (allergen or irritant)
- > ie. cold injury (frostbite, chillblains)
- Infection
- Trauma
- > ie. Dermatitis Artefacta
What are the internal causes of skin disease?
- Systemic disease
- Genetics
- > ie. neurofribromatosis, icthyosis
- Drugs:
- > vary in severity
- > think of OTC drugs
- > take a good drug history
- Infection
- Autoimmune
- > Bullous Pemphigoid
What is a Macule?
- Small, flat circumscribed area <5mm
- Non-palpable change in skin colour with distinct borders
What is a Patch?
Example/s?
- Larger, flat circumscribed area >5mm
- Non-palpable change in skin colour with distinct borders
- Hyper-pigmentation = congenital melanocytic naevus
- Hypo-pigmentation = vitiligo
What is a Papule?
Example/s?
- Small raised area, <1cm in diameter
- Palpable solid lesion
What is a Plaque?
Example/s?
- Larger raised area, >1cm in diameter
- Palpable, solid lesion
- ie. Untreated psoriasis
What is a Nodule?
Example/s?
- Palpable lesion, taller than it is wide
- ie. Neurofribromatosis, Rheumatoid nodules
What is a Vesicle?
Example?
- Small, fluid-filled, superficial, thin-walled cavity, <1cm in diameter
- ie. insect bite
What is a Bulla?
Example?
- Large, fluid-filled, superficial, thin-walled cavity, >1cm in diameter
- ie. Bullous Pemphigoid
What is a Pustule?
Example?
- Small, pus-filled, superficial, thin-walled cavity
- ie. Acne
What is an Abscess?
- Large, pus-filled, thick-walled cavity
What is an Erosion?
Example?
- Skin defect causing loss of Epidermis
- Heals w/o scarring (bc only confined to the Epidermis)
- ie. Toxic Epidermal Necrolysis
What is an Ulcer?
Example?
- Skin defect causing loss of Epidermis and Dermis
- Does not heal w/o scarring (as it affects all 3 layers)
- ie. Pyoderma Gangrenosum (ie. IBD (UC, CD), Arthritis)
What is the distribution of Acanthosis Nigricans, and what is it associated with?
- Flexural distribution
- > (ie. axillae, neck, elbow/knee creases
- Associated with: Insulin Resistance, Obesity, Malignancy
How would you describe the markings of Acanthosis Nigricans?
- Hyperkeratosis and Hyperpigmentation papules
- “Velvety” appearance
What is Pre-tibial Myxoedema associated with?
- Grave’s disease
What investigations might you arrange if you suspect a bacterial skin infection?
- Charcoal swab!!
- ask for MC+S!!
- > (Microscopy, Culture and Sensitivities)
What investigations might you arrange if you suspect a viral skin infection?
- Viral swab for PCR!!
- > swab the vesicle/bulla if vesicular eruption
- > if systemic illness -> VTS
What investigations might you arrange if you suspect a fungal skin infection?
- Skin scraping
- Nail clipping
- Hair sample
- send for Fungal cultures!! (mycology)
How are medicines licensed in the UK?
- MHRA - Medicines and Healthcare Products Regulatory Agency
- EMA - European Medicines Agency
- agree whether or not his medication is suitable to be used and get a license*
What is the SMC?
- Scottish Medicines Consortium
- decides where a drug is used in the NHS
What is an “unlicensed” drug?
- Not approved for use in the UK
What is an “off-label” drug?
- A licensed medication that is being used for an unlicensed indication
What is a “specials” drug?
- Unlicensed dermatological preparations
- Long history of use, no strong evidence base but clinically effective (ie. crude coal tar)
What are the common causes of prescription errors?
- Lack of knowledge
- > ie. about the pt., the med, and allergies
- Mistake writing/generating the prescription
- > ie. mg vs. mcg, % not written clearly
- Poor communication
- No local or national guidelines
- > ie. it is a rare medication
What are the factors associated with poor adherence?
- Psychiatric co-morbidities
- Slower-acting agents
- Multiple applications/day
- Lack of pt. education
- Cosmetic acceptability of treatments
- Unintentional non-adherence
- > ie. pt. may need information leaflet so they can self-manage their meds at home
What Pharmacodynamic factors do you need to be aware of when prescribing?
- basically pt. factors*
- Age of pt.
- Pregnancy risk
- Drug interactions
- Pharmacogenetics
ie. pt. may genetically have lower levels of a certain enzyme, which alters drug metabolism
What Pharmacodynamic factors do you need to be aware of when prescribing?
- route of Administration
- > topically where possible
- > if oral, optimal absorption important (ie. some meds need to be taken with a fattier meal to optimise absorption)
- Distribution - where the drug goes
- Metabolism - esp. in Liver disease
- Excretion - esp. in Renal disease
What factors affect Topical Absorption?
- Concentration
- Base/vehicle
- Chemical properties of the drug
- Thickness and hydration of stratum corneum
- Temperature
- Skin site
- Occlusion (ie. wrapping something around the area that the cream is applied to)
What type of topical therapy is best for feet?
- Spray powder!!
What type of topical therapy is best for the scalp?
- Shampoo!!
What type of topical therapy is best for the finger?
- Wart paint!!
What is the mode of action of Topical Steroids?
- Regulates pro-inflammatory cytokines
- Suppresses fibroblasts, endothelial and leukocyte function
- Vasoconstriction
- Inhibits vascular permeability
What is the Finger Tip Unit? What does it equate to?
What surface area does it cover?
- Unit of measurement used for the application of topical steroids
- about 0.5g (to the distal skin crease)
- Should treat an area double the size of one hand
What are the Side-effects of Topical Steroids?
- Skin thinning/atrophy
- Striae
- Bruising
- Hirsutism
- Telangiectasia
- Acne/Rosacea/Peri-oral Dermatitis
- Glaucoma
- Cataracts
- Systemic absorption
What is the mechanism of action of Retinoids?
- Vitamin A analogues
- Normalise keratinocyte function
What are the indications for Retinoids?
- 4 different molecules used orally in Dermatology*
- Acne -> isotretnoin (roaccutane)
- Psoriasis -> acitretin
- Cutaneous T cell Lymphoma -> bexarotene
- Hand eczema -> alitretinoin
What are the adverse effects of Retinoids?
- Teratogenic
- > don’t use in pregnant pts/women of child-bearing age
- Chellitis (dry lips), Xerosis (dry skin)
- Increased transaminases and triglycerides
- rarely: Psychiatric, eye, bone side effects
- therefore can only be prescribed in hospitals as needs monitoring, NOT by GPs!!*
What are the adverse effects of Immunosuppressants?
- ie. oral steroids, azathioprine, ciclosporin, methotrexate, mycophenolate mofetil*
- Risk of malignancy and serious infection
- Need regular blood monitoring: esp. FBC (methotrexate, azathioprine), Renal function (ciclosporin) and Liver function (methotrexate)
What are the adverse effects of Immunosuppressants?
- Psoriasis
- Hidradenitis suppurativa
- Chronic Spontaneous Urticaria
- Atopic Eczema
- Pemphigus
- MELANOMA
What are the adverse effects of Biologics?
- Risk of infection
- > TB reactivation
- > serious infection
- > avoid live vaccines
- Risk of malignancy
- TNF inhibitors - risk of demyelination (nb. FH of MS)
Where can you get reliable information about different drugs used in Dermatology?
- SPC - Supplementary Protection Certificates
- SMC - Scottish Medicines Consortium
- BNF
- BAD guidelines - British Association of Dermatologists
- Local Formulary
