Efficacy and Safety of Azelaic Acid (AzA) Gel 15% in the Treatment of Post-Inflammatory Hyperpigmentation and Acne: A 16-Week, Baseline-Controlled Study

Acne vulgaris affects people of all ethnicities and races in the United States with little difference in pathophysiology. ¹ One report in the United Kingdom showed that acne vulgaris is the most common dermatologic diagnosis among adult black patients.² Another study from 1965 revealed that nine percent of black patients had acne versus 18 percent of white patients.³ Halder and his group reported that acne was the most common diagnosis in both black and white patient populations: 29.5 percent of white patients compared to 27.7 percent of black patients.⁴ The fact that patients with skin of color may seek treatment at lower rates than white patients may affect these results. Therefore, efforts to identify differences in the frequency of acne in skin of color have failed to provide conclusive evidence.⁵ While the pathophysiology of acne is invariable across all skin types, there is some evidence to suggest that black patients may have larger sebaceous glands⁶ and increased sebum production compared to whites.^5,7 Nonetheless, the experience of acne among patients with darker skin (Fitzpatrick skin types IV to VI) may differ because these individuals are more susceptible to post-inflammatory hyperpigmentation (PIH), a common and troubling antecedent of acne.^1,5

Treatments for PIH are available, but their efficacy and suitability are not optimal. For example, topical tretinoin, a first-line treatment for mild-to-moderate acne has been shown to reduce the appearance of post-inflammatory hyperpigmentation, but it was also shown to lighten normal skin.⁸ Additionally, topical retinoids are known to contribute to PIH by causing irritation. Azelaic acid (AzA), a naturally occurring dicarboxylic acid with anti-inflammatory, antimicrobial, antikeratinizing, antioxidant and antityrosinase mechanisms of action^9,10 may be ideal for both the management of acne and treatment of PIH associated with it. AzA's anti-inflammatory, antimicrobial and antikeratinizing effects have been shown to be beneficial in the topical treatment for acne.¹¹ Thought to inhibit the synthesis and release of melanin,^10,12 AzA has direct anti-tyrosinase activity that has demonstrated efficacy in the management of PIH.¹³ An AzA cream 20% formulation has been approved for acne vulgaris, while AzA gel 15% has been approved for papulopustular rosacea. While AzA has been used clinically for the management of acne and associated PIH, this study is the first to assess the effects of AzA gel 15% on both acne and PIH in patients with skin of color.

This single-center, open-label, IRB-approved pilot study was conducted over 16 weeks. Adults (n=20) with mild-to-moderate acne and moderate-to-severe PIH and Fitzpatrick skin type IV