Tretinoin — Topical retinoid (Vitamin A acid) — retinoic acid receptor agonist

The "retinization" phase (first 6-12 weeks) of erythema, peeling, and sensitivity is often misinterpreted as skin damage — it actually reflects accelerated epidermal turnover. This phase resolves as the skin adapts. Key prescribing points: (1) Apply to completely dry skin 20-30 minutes after washing (wet skin increases penetration and irritation); (2) Always use broad-spectrum SPF 30+ daily; (3) Avoid concurrent use of benzoyl peroxide (inactivation) without buffering; (4) Pregnant patients must stop — Accutane (isotretinoin) has a mandatory iPLEDGE program. Prescription-strength tretinoin is significantly more effective than over-the-counter retinol (conversion to retinoic acid is inefficient and variable with retinol).

Overview

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Compound Class

Topical retinoid (Vitamin A acid) — retinoic acid receptor agonist

Mechanism of Action

Binds nuclear retinoic acid receptors (RAR-α, RAR-β, RAR-γ) regulating transcription of genes involved in keratinocyte differentiation, collagen synthesis, and matrix metalloproteinase inhibition. Key mechanisms: (1) Increases epidermal turnover — reduces corneocyte cohesion, accelerates desquamation, increases stratum corneum thickness over time; (2) Stimulates procollagen I/III synthesis in dermis via TGF-β pathway; (3) Inhibits collagenase (MMP-1) — prevents UV-induced collagen degradation; (4) Increases glycosaminoglycan deposition; (5) Normalizes abnormal keratinocyte differentiation (acne mechanism); (6) Reduces tyrosinase activity and melanosome transfer (hyperpigmentation). Gold standard for photoaged skin — only topical agent with randomized controlled trial evidence for wrinkle reduction.

Regulatory Status

FDA approved — Retin-A (acne), Avita (acne/keratosis), Renova/Refissa (photodamage/fine lines)

Evidence Level

High — decades of RCT evidence for photodamage; FDA-approved for acne and actinic keratosis; Kligman's original 1986 NEJM paper established photoaging reversal evidence