What is the rationale for using a macrolide to treat pityriasis rosea (PR)?
—Michelle Spencer, NP, Salt Lake City
PR is a papulosquamous dermatosis. Classically, the condition presents with a single large lesion (herald patch). Within a few days to a few weeks, multiple additional smaller lesions appear along the cleavage lines (Langer’s lines). The duration of the dermatosis ranges from two to 10 weeks (Am Fam Physician. 2004;69:87-91). A double-blind, placebo-controlled clinical trial randomized 90 PR patients to erythromycin (as tablets or syrup) daily for two weeks (1 g in four equally divided doses in adults and 25-40 mg/kg/day in four divided doses in children) or to placebo. After two weeks, 33 of 45 patients (73%) treated with erythromycin demonstrated complete response (J Am Acad Dermatol. 2000;42:241-244). The rationale for using a macrolide antibiotic (such as erythromycin) to treat PR was based on the hypothesis that this condition may be caused by an infectious agent sensitive to erythromycin or may be related to the anti-inflammatory properties of the antibiotic or both.
However, a more recent trial with another macrolide antibiotic (azithromycin at a dose of 12 mg/kg/day, up to a maximum of 500 mg/day for five days) vs. placebo in 49 children with PR demonstrated that the rates of cure and partial resolution were similar in the azithromycin and placebo groups (Pediatrics. 2006;117:1702-1705).
—Philip R. Cohen, MD (107-11)