DERM DRUGS

Question 1

Benzoyl Peroxide (3% and 5%)
Mixed with Clindamycin (DUAC)

Answer 1

I: Acne >12yrs
MOA: Exhibits bactericidal effect against cutiibacterium acne.
Peroxide bond of benzoyl peroxide is cleaved to form 2 benzoyloxy radicals. These interact with bacterial proteins; interfering with their function and survival of the bacteria. Over time, free radical interactions with the bacterial proteins lead to decreased keratin and sebum around follicles.
SE: Skin irritation (dryness, discomfort, erythema, peeling, blistering), increase risk of sunburn, bleaching of hair and fabrics
CI: broken skin, eyes, mouth and mucous membrane, hypersensitivity
KI: alternate between topical drugs
PC: Can cause redness and peeling- occur initially but settle with time.
Wear sunscreen as it can increase risk of sunburn. Apply at night and wash off in the AM
To reduce irritation, start of slowly e.g 1st day 30 mins, 2nd day 1hr and eventually throughout the night.
Can bleach fabrics and hair so be careful

Question 2

Topical retinoids

Adapalene and Tretinoin

Answer 2

I: Acne Vulgaris
MOA: Modulates cellular keratinisation and inflammatory process
SE: Skin irritation (discomfort, blistering of skin, crusting, dryness, erythema, pruritis), eye irritation, increased sensitivity to UV light
CI: Pregnancy, Breastfeeding, Severe acne (rosacea, peri oral dermatitis), FHX of non melanoma skin cancer
KI: Other retinoids with similar MOA, abrasive cleaners, comedogenic or astringent cosmetics
PC: If separate products are used then apply 12 hours apart. Topical retinoids at night - the other in the morning
Apply once daily or twice daily
Use sparingly and not just on visible spots
Sensitive skin - lower dose and titrate as tolerated
Concomitant use of a noncomedogenic moisturiser and sunscreen may help tolerability

Question 3

Topical ABX

Clindamycin and Erythromycin

Answer 3

ALWAYS PRESCRIBED WITH BENZOYL PEROXIDE
SE: Skin irritation (dryness, erythema), urticaria, folliculitis. Clindamycin can cause anaphylactic shock, hypotension, oesophageal ulcers, oesphagitis, abnormal LFTS
C: pregnancy, atopy, hypersensitivity, hx of IBD/ ABX - associated colitis - if diarrhoea occurs stop using immediately
KI: CYP inducers (rifampicin -> reducing efficacy)
ABX prep for acne containing alcohol not suitable with benzoyl peroxide

Question 4

Azelaic Acid

Answer 4

I: Acne
SE: Skin reaction (discomfort, erythema, peeling, dermatitis). Exacerbates asthma, angioedema, eye swelling.
CI: avoid eye, mouth and mucous membrane contact
C: Breastfeeding and pregnancy
PC: Apply twice daily - if sensitive skin apply once daily for 1/52 until irritation ceases then apply twice daily - temporarily interrupt treatment for a few days if required
Avoid contact with eyes and mouth
If PMHx of asthma and they feel SOB, wheezy, unable to speak in full sentences -> go A+E

Question 5

ORAL ABX

Lymecycline, Doxycycline, Oxytetracycline

Answer 5

I: Used if topical treatment fails or acne is severe + scarring

Give macrolide ABX (erythromycin) ONLY if tetracycline is contraindicated (Pregnancy)
A topical retinoid or benzoyl peroxide should always be co-prescribed with oral antibiotics to reduce risk of ABX resistance developing
- However never use them both together

CI: Hypersensitivity, tetracycline is contraindicated in pregnant or breastfeeding women and children <12 yrs.
Lymecycline is contraindicated in children <8 yrs

SE: Anaphylaxis, angioedema, photosensitivity, rash, diarrhoea, dysphagia, headache, nausea, vomiting,
Serious SE: blood disorders, ABX associated colitis, Steven’s Johnson syndrome.
Erythromycin -> abdo pain, diarrhoea, N+V, rash, arrhythmias, QT interval prolongation, Steven-Johnson syndrome

Question 6

Topical Steroids
Moderate (Clobetasone Valerate - Emovate)
(Betamethasone Valerate 0.025%)

Potent* (Betamethasone Valerate 0.1%)
(Mometasone Furoate 0.1% - Elocon)

Very Potent* (Clobetasol Propionate 0.05%)

Answer 6

I: Eczema
MOA: Immunosuppressive, metabolic and mineralcorticoid effects
SE: Skin thinning, striae, telangiecasia, contact dermatitis.
Withdrawal of corticosteroid can cause a rebound worsening of underlying skin.
Rare adrenal supporession and systemic adverse effects
C: Infection present, facial lesions
KI: Space out application to allow absorption of agent. Apply emollient last.
PC: Relieves inflammation and improves skin problems
Emollient first then wait 15-30 mins to absorb into skin then apply steroid cream.
If flaring, continue treatment 48hrs after eczema has cleared. If not improved in 2/52, come back in.
Apply sparingly to affected areas using FTU.

FTU
Arm Hand: Adult: 4, children 2.5 
Leg/ foot: Adult 8, children 4.5
Trunk (front): Adult 7, children 3.5
Trunk (back): Adult 7, children 5