Topical Therapies for Acne
Topical treatment is a key component of acne therapy. Acne treatments target factors contributing to acne formation and act to normalize follicular keratinization and decrease sebaceous gland activity and follicular bacterial populations [1]. With early t
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Topical Therapies for Acne Mary-Margaret Kober, Whitney P. Bowe, and Alan R. Shalita
3.1
Introduction
Topical treatment is a key component of acne therapy. Acne treatments target factors contributing to acne formation and act to normalize follicular keratinization and decrease sebaceous gland activity and follicular bacterial populations [1]. With early treatment, acne scarring, post-inflammatory hyperpigmentation, and psychological distress may be reduced or prevented [2]. Topical therapies for acne come in prescription and over-the-counter formulations. This chapter will focus on prescription products only.
3.2
Topical Retinoids
Biologically active molecules derived from vitamin A, topical retinoids have become a mainstay in acne therapy. Retinoids bind retinoic acid receptors (RARs) and retinoic X receptors (RXRs). Three subgroups of RARs exist: RAR-α (alpha), RAR-β (beta), and RAR-γ (gamma). RAR-α (alpha) is expressed throughout adult and embryonic tissue. RAR-β (beta) resides in dermal fibroblasts, and RAR-γ (gamma), present throughout the epidermis, is likely the receptor responsible for the positive effects retinoids exert on keratinocytes [3]. Once bound to their receptor, retinoids promote proliferation of basal keratinocytes, block the terminal stages of epithelial differentiation, and reduce filaggrin expression and proteolysis of keratins 1 and 14 [4]; these changes normalize keratinization and prevent the hyperproliferative state associated with comedo formation [5, 6]
M.-M. Kober, M.D. (*) • W.P. Bowe, M.D. • A.R. Shalita, M.D. Department of Dermatology, SUNY Downstate Medical Center, 450 Clarkson Road, Brooklyn, NY, USA e-mail: [email protected]; [email protected]; [email protected] J.A. Zeichner (ed.), Acneiform Eruptions in Dermatology: A Differential Diagnosis, DOI 10.1007/978-1-4614-8344-1_3, © Springer Science+Business Media New York 2014
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Currently, four topical retinoids are available: tretinoin, isotretinoin, tazarotene, and adapalene. However, only tretinoin, tazarotene, and adapalene are available in the United States.
3.2.1
Tretinoin (First-Generation Retinoids)
Tretinoin is the oldest of the retinoids and binds with equal affinity to all RAR receptors. Tretinoin demonstrates superiority to benzoyl peroxide (BP), sulfurresorcinol, and vehicle in the reduction of inflammatory and noninflammatory acne lesions as well as the global severity of acne [7, 8]. Although there may be some improvement noted after 2–3 weeks, the most significant reduction in acne lesions is noted after 3–4 months of consistent use [9]. The histopathologic findings seen in skin receiving tretinoin include acanthosis, parakeratosis, and thinning of the stratum corneum [8], which correlates with the observation that the tretinoin-induced thinning of the stratum corneum allows for improved efficacy of topical antimicrobial products [10]. Ultraviolet light and oxidants such as benzoyl peroxide degrade tretinoin upon exposure [9]. Advances in formulation technology have allowe
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