Pharmacologic class: Sulfone
Active ingredient: Dapsone 5%; gel.
Indication: Topical treatment of acne vulgaris.
Pharmacology: Dapsone is an antibacterial agent that is used systemically to treat infections such as leprosy and dermatitis herpetiformis; it is thought to work by interfering with the folate metabolism of susceptible organisms. The mechanism of action of dapsone in the treatment of acne is not understood; however, it is believed to have anti-inflammatory properties.
The oral use of dapsone has been associated with peripheral neuropathy, severe skin reactions (e.g., toxic epidermal necrolysis), and hemolytic anemia. Patients with G6PD deficiency are more prone to hemolysis with the use of certain drugs. However, the limited systemic exposure resulting from the topical use of dapsone is not likely to result in hematologic or other systemic toxicity. Some patients with G6PD deficiency developed laboratory evidence of mild hemolysis with the topical use of dapsone gel 5%, but none of the cases involved clinically relevant hemolysis or hemolytic anemia.
Clinical trials: The efficacy of topical dapsone gel 5% in treating acne vulgaris was evaluated in two double-blind studies. Patients >12 years of age who had 20-50 inflammatory lesions and 20-100 noninflammatory lesions were enrolled. Either dapsone gel 5% or vehicle was applied twice daily for up to 12 weeks. The Global Acne Assessment Score and the percent reduction in lesions (inflammatory, noninflammatory, and total) were used to evaluate efficacy. The Global Acne Assessment Score is composed of a five-point scale ranging from “0” (no evidence of facial acne vulgaris) to “4” (severe acne with a significant degree of inflammatory disease).
At week 12, 42% and 35% of patients using dapsone aqueous gel 5% had no or minimal acne in the two studies, compared with 32% and 28% for those using vehicle, respectively. Patients in Study 1 had a 38% reduction in total lesions from baseline to week 12, and those in Study 2 had a 37% reduction, compared with 32% and 29% for those using vehicle, respectively. Female patients generally had a greater percent reduction in lesions and greater success in the Global Acne Assessment Scale. Across racial subgroups, the efficacy results were similar.
Adults and children: <12 years: not recommended. >12 years: Wash skin and pat dry. Apply pea-sized amount to affected area in a thin layer twice daily in the am and pm. Rub in gently and completely. Wash hands after use. Re-evaluate if no improvement after 12 weeks.
Precautions: G6PD deficiency; may have increased risk of hemolytic anemia. Discontinue if evidence of hemolytic anemia occurs. Pregnancy (Cat. C). Nursing mothers: not recommended.
Interactions: Concomitant trimethoprim/sulfamethoxazole, other folic acid antagonists (e.g., pyrimethamine), anticonvulsants, rifampin, St. John’s wort: increased risk of hemolysis in G6PD deficient patients. Skin/hair discoloration with topical benzoyl peroxide.
Adverse reactions: Application site reactions (dryness, oiliness, redness, peeling); rarely: psychiatric reactions, GI reactions, pharyngitis.
How supplied: Gel—30 g.
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