Adapalen: Effect as Retinoid in Acne

Adapalen (trade names Differin, Epiduo in combination with benzoyl peroxide, and generics) is a third generation synthetic retinoid specifically developed for topical application. In Germany, adapalen is an established first-line therapy for mild to moderate acne vulgaris as recommended in clinical guidelines. Compared to classic retinoids such as tretinoin or isotretinoin (oral), adapalen has a more favourable tolerability profile with comparable efficacy because it binds more selectively to retinoid receptor subtypes.

The active ingredient is available in 0.1 percent and 0.3 percent concentrations as a cream or gel, alone or in combination with benzoyl peroxide (2.5 or 3 percent). These combination products address multiple acne pathogenic mechanisms simultaneously and are particularly effective in practice. The therapy is designed for consistent application over several weeks because initial visible improvements often appear only after approximately four to eight weeks.

Mechanism of Action

Adapalen selectively binds to the nuclear retinoid receptors RAR beta and RAR gamma in keratinocytes. It normalizes the differentiation and keratinization of sebaceous gland ducts, reduces the formation of microcomedones, and dissolves existing comedones. This comedolytic and anti-comedogenic effect forms the basis of acne therapy.

In addition, adapalen exerts anti-inflammatory effects by reducing the activity of neutrophil granulocytes and inflammatory mediators such as leukotrienes and prostaglandins. A modulating effect on sebum secretion through changes in lipid composition has also been described, although adapalen has less anti-seborrheic activity than isotretinoin.

Systemic absorption after topical application is very low because adapalen is lipophilic and poorly absorbed through intact skin. Plasma levels are usually below the detection limit, so clinically relevant systemic effects practically do not occur. Nevertheless, all retinoids should be used restrictively during pregnancy.

Indications

• Acne vulgaris in comedonal, papulopustular, and mild to moderate forms
• Maintenance therapy after successful acne resolution to prevent recurrence
• Off-label use in actinic keratosis, photoaging, pseudofolliculitis barbae, and certain pigmentation disorders, individual indication
• Off-label use in adjuvant therapy of hidradenitis suppurativa in early stages, individual cases

Adapalen is not indicated for acne conglobata, acne fulminans, or in patients already receiving systemic isotretinoin therapy. In cases of deep inflammatory nodules and cysts, additional systemic measures such as oral antibiotics or isotretinoin are usually necessary.

Dosage and Application

Adapalen 0.1 percent gel or cream: apply once daily in the evening to cleansed and dry skin, thin layer over the entire affected area, not just individual spots.

Adapalen 0.3 percent gel: for more severe acne according to individual prescription, also applied once daily in the evening.

Combination products (adapalen plus benzoyl peroxide): once daily in the evening, same application technique. The combination is usually more effective than individual active ingredients.

First weeks: due to the skin-irritating effect, application can initially be reduced to every other or every third evening, with gradual increase to daily use.

Cleansing: use mild non-irritating cleansers, avoid harsh toners, alcohol-containing lotions, and intense scrubbing because irritation otherwise accumulates.

Sun protection: consistently use sun protection factor of at least 30 during the day because adapalen increases light sensitivity.

Duration of therapy: initial visible improvements often after 4 to 8 weeks, full effect after 12 weeks. Maintenance therapy for several months is advisable.

Adverse Effects

Very common: skin dryness, scaling, redness, burning or stinging after application, pruritus, worsening of acne in the first two to four weeks (so-called initial reaction).

Common: contact dermatitis, local skin irritation, photosensitivity, temporary hyperpigmentation in dark skin types.

Uncommon to rare: swelling, skin discoloration, allergic reactions.

Initial reaction: in the first two to four weeks, the skin appearance may seem to worsen because deeply situated microcomedones come to the surface. This phase is normal and temporary.

Eyes and mucous membranes: do not apply to eyes, lips, or nasal mucous membranes because pronounced irritation may occur.

Drug Interactions

• Other retinoids (topical tretinoin, tazarotene): combination usually unnecessary and highly irritating to skin.
• Salicylic acid and alpha hydroxy acids: additional irritation potential, combined use intensifies skin redness and scaling.
• Topical antibiotics (clindamycin, erythromycin): meaningful combination in inflammatory acne, often available as fixed combination.
• Benzoyl peroxide: optimized in combination products, when applied separately it can inactivate adapalen oxidatively, therefore ideally applied at different times or as fixed product.
• UV exposure and tanning beds: increased photosensitivity, consistent sun protection, avoid sunburn.
• Skincare products with alcohol or astringents: intensify dryness and irritation.

Special Precautions

Pregnancy: Adapalen is not recommended during pregnancy because systemic retinoids are teratogenic and there is very limited data for topical retinoids. Women of childbearing age should use reliable contraception or discontinue the product if pregnancy occurs. Breastfeeding: avoid application on large skin areas and in the breast region.

Children: approved from 9 or 12 years of age depending on the product, when acne is clearly diagnosed.

Before starting therapy: history of skin diseases, allergies, other topical agents, planned UV exposure, cosmetic routine. Patient education regarding initial reaction, gradual dose escalation, and consistent sun protection.

Lifestyle: acne is exacerbated by comedogenic cosmetics, mechanical irritation (helmet chin straps, telephone receivers on the skin), certain sports with sweating, and unsuitable skincare. Adapted, mild, hydrating care supports the therapy.

When to consult a dermatologist: in cases of deep inflammatory nodules, scarring, extensive acne over multiple areas, psychological burden, or lack of improvement after three months, specialist evaluation is advisable. Here, systemic therapy with antibiotics or isotretinoin can be discussed.

Driving ability: not impaired by topical application.

You May Also Be Interested In

• Isotretinoin, systemic retinoid for severe acne
• Clindamycin, topical and systemic antibiotic in acne therapy
• Doxycycline, oral tetracycline for moderate acne
• Dexpanthenol, skin regenerating care for retinoid-induced dryness
• Nicotinamide, Vitamin B3 for acne and skin barrier dysfunction

Frequently Asked Questions

Sources

• Gelbe Liste, Adapalen active ingredient profile
• BfArM, Federal Institute for Drugs and Medical Devices
• AWMF, S2k Guideline Acne
• German Dermatological Society