Topical Retinoids
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Direct answer
Topical retinoids are vitamin A derivatives, including tretinoin, adapalene and tazarotene, that bind nuclear retinoic acid receptors to normalise follicular keratinisation. They reduce comedones and inflammation in acne, and tazarotene is also used for plaque psoriasis. Their main adverse effect is retinoid dermatitis, with erythema, scaling and burning, and they are avoided in pregnancy as a precaution.
What you must remember
- Mechanism: binds retinoic acid receptors in keratinocytes, normalising follicular keratinisation and reducing microcomedone formation.
- Tretinoin: all-trans retinoic acid, used at 0.025 to 0.1 percent, the classic comedolytic and more irritating than adapalene.
- Adapalene: 0.1 percent gel, generally better tolerated and more stable in sunlight than tretinoin.
- Tazarotene: used for acne and plaque psoriasis, and contraindicated in pregnancy.
- Retinoid dermatitis: erythema, scaling, dryness and burning, most marked in the first few weeks.
- Photosensitivity: all retinoids increase sunburn risk, so daily sunscreen is required.
- Acne role: retinoids treat comedones and underlie inflammatory lesions, and are combined with benzoyl peroxide or a topical antibiotic.
Starting and sustaining a topical retinoid
Most failures with topical retinoids come from early stopping rather than lack of efficacy. The sequence below prevents the common errors and sets expectations for the patient.
- Choose the agent: tretinoin for strong comedolysis, adapalene for better tolerability, and tazarotene for selected acne or psoriasis cases.
- Start low: begin with a lower concentration, or apply on alternate nights, for the first few weeks.
- Apply sparingly: use a pea-sized amount to the whole affected area at night, avoiding the eyes, nose and mouth corners.
- Use a moisturiser: a bland moisturiser reduces dryness and irritation without reducing efficacy.
- Protect from the sun: daily broad-spectrum sunscreen is needed, because retinoids increase photosensitivity.
- Expect an early phase: a transient worsening over the first few weeks is common, and treatment is usually continued unless irritation is severe.
In acne, a response commonly takes around eight to twelve weeks, so an early review should judge adherence rather than efficacy.
Where the exam tries to catch you
Retinoid questions often test the timing of response, the irritation pattern and the pregnancy rule.
- Trap: expecting tretinoin to work within days Correct: the comedolytic benefit takes weeks, and early worsening is common, so the drug is continued unless irritation is severe.
- Trap: treating topical retinoids as antibiotics for inflammatory acne Correct: they target comedones and keratinisation, so they are paired with benzoyl peroxide or a topical antibiotic for inflammatory lesions.
- Trap: ignoring pregnancy status when prescribing tazarotene Correct: tazarotene is contraindicated in pregnancy, and other topical retinoids are avoided as a precaution.
Frequently asked questions
What is the mechanism of tretinoin in acne?
Tretinoin binds nuclear retinoic acid receptors in follicular keratinocytes, normalising keratinisation and reducing microcomedone formation. It also reduces some inflammatory mediators. The result is fewer comedones and a gradual improvement in acne.
Why does retinoid dermatitis occur with topical retinoids?
Retinoid dermatitis occurs because topical retinoids increase epidermal turnover and irritate the skin, producing erythema, scaling, burning and dryness. Tretinoin is more irritating than adapalene. Starting at a low concentration and using a moisturiser reduce the severity of retinoid dermatitis.
Is adapalene better tolerated than tretinoin?
Adapalene is generally better tolerated than tretinoin, with less irritation and better stability in sunlight. Its efficacy in comedonal acne is broadly comparable. Both need sun protection and a gradual introduction.
Can topical retinoids be used in pregnancy?
Topical retinoids are generally avoided in pregnancy as a precaution, and tazarotene is contraindicated. Systemic retinoids such as isotretinoin carry a much greater teratogenic risk. Pregnancy status should be checked before prescribing any topical retinoid to a woman of reproductive age.