Topical Acne Therapies

Topical acne therapies treat the four drivers of acne: abnormal follicular keratinisation, excess sebum, Cutibacterium acnes proliferation, and inflammation. They are first-line treatment for mild to moderate acne and are combined with systemic therapy in moderate to severe disease.

Mechanism. Retinoids normalise keratinisation and reduce comedones; benzoyl peroxide is bactericidal through free radical release and mildly comedolytic, with no known bacterial resistance; azelaic acid is antimicrobial, comedolytic, anti-inflammatory and inhibits tyrosinase; salicylic acid is keratolytic; clindamycin and erythromycin are bacteriostatic and mildly anti-inflammatory; dapsone is anti-inflammatory; clascoterone is a topical androgen receptor inhibitor.

Pharmacokinetics. Low systemic absorption for all topical agents at normal use.

• Benzoyl peroxide 2.5 to 10 percent: wash, gel or cream; bleaches hair and fabrics.
• Topical retinoids: adapalene 0.1 to 0.3 percent, tretinoin, tazarotene, trifarotene.
• Azelaic acid 15 percent gel or 20 percent cream: useful in darker skin and post-inflammatory hyperpigmentation; acceptable in pregnancy.
• Topical antibiotics: clindamycin 1 percent, erythromycin 2 to 4 percent; always combined with benzoyl peroxide or a retinoid.
• Salicylic acid 0.5 to 2 percent: mild comedonal acne.
• Dapsone 5 percent gel: inflammatory acne.
• Fixed combinations: adapalene with benzoyl peroxide; clindamycin with benzoyl peroxide; clindamycin with tretinoin.
• Clascoterone 1 percent cream: twice daily; limited availability.

Selection by severity.

• Comedonal acne: topical retinoid (adapalene 0.1 percent) alone.
• Mild to moderate inflammatory acne: benzoyl peroxide 2.5 to 5 percent with a topical retinoid, or a fixed combination, once daily at night (benzoyl peroxide may also be used in the morning).
• Add a topical antibiotic only in combination with benzoyl peroxide, for no longer than 12 weeks, to reduce bacterial resistance.
• Azelaic acid 15 to 20 percent twice daily as an alternative for intolerance, pigmentation and pregnancy.
• Apply to the whole affected area, not individual spots. Review at 8 to 12 weeks; continue a retinoid as maintenance.
• Add systemic treatment for moderate to severe, scarring or psychologically distressing acne.

Contraindications. Hypersensitivity; benzoyl peroxide allergic contact dermatitis; azelaic acid caution with asthma (rare irritation).

Effects. Dryness, erythema, peeling and stinging in the first 2 to 4 weeks; bleaching of clothing and hair with benzoyl peroxide; bacterial resistance to topical clindamycin and erythromycin when used alone; photosensitivity with retinoids.

Interactions. Benzoyl peroxide oxidises tretinoin; avoid other irritants.

Monitoring. Review at 8 to 12 weeks; assess tolerance, pigmentation and scarring; reduce frequency if irritation limits use.

Special groups. Pregnancy: azelaic acid, benzoyl peroxide and clindamycin are acceptable; topical retinoids are avoided (tazarotene contraindicated). Breastfeeding: acceptable away from the nipple. Children: from about 12 years (adapalene from about 9). Region: post-inflammatory hyperpigmentation is common in darker skin, so start gently, protect against the sun, and avoid harsh irritants and unregulated lightening products.