Dermatology Questions
- What are the physiological barriers in the skin?
Stratum Corneum outer layer- dry skin
- 10-15 layer of corneocytes/tightly packed cell layers
( (cells contain keratin)
Viable epidermis -maintaining integrity, cell healing, immune defence (no
blood supply)
Dermis
Subcutaneous fat – insulation/mechanical protection
- What are the different factors that are influencing drug penetration into the skin?
Transappendageal (shunt route)- sweat ducts offer ores to the dermis
Transcellular – polar route for hydrophilic molecules
Intercellular – less polar route for hydrophobic molecules
-Age, ethnicity, skin hydration(increases penetration for both hydrophilic/phobic molecules,
skin thickness, body site (palms of hand and sole of feet thickest), pathological disorders.
-Drug molecular weight, Partition coefficient between vehicle and skin (Log P between 1&3/
if drug >3 accumulation in stratum corneum),pKa, concentration gradient.
-Occlusion: ointment and w/o creams prevent water evaporation from the skin (increase
hydration and drug permeation)
Many components have permeation enhancers properties Chemical agents which
decrease the barrier properties of the
stratum corneum without damaging the underlying cells. Fatty acids, surfactants,Urea.
- What are the strategies to improve drug penetration to the skin?
Use of prodrugs: attachment of lipophilic moieties (increase partitioning) into stratum
corneum which are usually esters cleaved by esterase to release parent molecule.
(Dramatically increases skin penetration but toxicity unknown.
,E.g. Betamethasone/hydrocortisone
- What are the different types of formulations for topical delivery, advantages,
drawbacks?
Liquid formulations
Solutions - typically contain co-solvents, surfactants, thickening agents.
Emulsions – droplets of one liquid dispersed in another liquid with the help of mixed
surfactants.
water in oil – unstable
Advantages/drawbacks of lotions
-Runny, not greasy, can dry the skin.
-Creams - Semi-solid emulsions easy to spread on the skin and not too greasy.
-O/W can be used for wounds, bites, acute inflammation,
-Ointments – continuous hydrophobic phase made of Gels - Continuous liquid phase
(polar or non–polar) thickened by polymers.
-Cooling feeling on the skin good for acute skin inflammation
Occlusive
good for dry skin conditions
Do not contain preservatives or surfactants.
Very greasy!
Taking a clinical history
,Diagnosis is based on:
-Clinical history
-Physical examination
-Investigation
Key components of a clinical history
• Presenting illness (complaint) (PC) and History of Presenting
Complaint (HPC)
• Past medical history (PMH)
• Family history (FH)
• Social history (SH)
• Drug history (DH) (previous/other illnesses)
• Systems review
• Person’s ideas and concerns
Skin infections
describe, diagnose and treat/refer the following skin infections:
Impetigo – itchy, Lil painful, heals 2/3 weeks once crust dried,
Diagnosis - thin walled vesicles or pustules (non-bullous)
- flaccid fluid filled vesicles and blisters (bullous impetigo)
Treatment/referral:
- Localised non-bullous = hydrogen peroxide 1%
cream or fusidic acid cream for 5 days.
-Widespread (≥4 clusters) = oral flucloxacillin or
Clarithromycin/erythromycin if allergic.
Shingles (herpes zoster)
-Caused by the reactivation of varicella zoster virus (chicken pox)
- prodromal phase with abnormal skin sensations and pain in the affected
dermatome (area of skin served by an individual nerve). Described as burning,
stabbing, or throbbing; Headache, photophobia, malaise, and fever (less
common) may also occur as part of the prodromal phase.
-Within 2–3 days (more rarely up to 7 days), a rash typically appears in a dermatomal
distribution
, -New vesicles continuing to form over 3–5 days. The rash is usually painful, itchy,
and/or tingly, and, unlike other rashes, does not cross the midline of the body.
-The vesicles then burst, releasing varicella-zoster virus, and crust over within 7–10
days.
-Healing occurs over 2–4 weeks, and often results in scarring and permanent
pigmentation in the affected area.
Complications and referral
Post-herpetic neuralgia
Refer to hospital if shingles in the trigeminal nerve or if the patient is severely
immunocompromised
A&E if meningitis or encephalitis suspected
Treatment
Assess pain and offer treatment
Paracetamol/co-codamol/NSAID
Refer to GP if these do not control pain
Aciclovir (or valaciclovir if immunosuppressed)
Infected insect bites
Patient usually will know if they have been bitten. Itchy, painful, swollen.
Risk factors for insect bites or stings such as occupation, contact with domestic pets,
camping, gardening, or walking in wooded/heath areas.
Check for signs of hypersensitivity:
Symptoms and signs of a mild SR include pruritus(itching) , urticarial(hives),
erythema(redness), mild angioedema(swelling beneath skin), rhinitis, and
conjunctivitis.
Symptoms and signs of a moderate SR include mild asthma, moderate angio-
oedema, abdominal pain, vomiting, diarrhoea, and mild, transient light headedness or
dizziness.
- Complications or referral:
- Consider calculating NEWS2
- Signs of anaphylaxis = 999, administer adrenaline
- Rule out DVT
Treatment:
- Self care: oral antihistamine and/or topical steroids OTC and safety netting advice
