Acyclovir is not effective in pityriasis rosea: Results of a randomized, triple-blind, placebo-controlled trial

Acyclovir is considered to be an effective treatment for pityriasis rosea but randomized, blinded, placebo-controlled trials have not been performed.

To test the efficacy of acyclovir in pityriasis rosea in a randomized, triple-blind, placebo-controlled trial.

Twenty seven patients with pityriasis rosea were randomly allocated to receive placebo (n = 13) or acyclovir (800 mg five times daily for one week) (n = 14). The severity of disease was assessed by the pityriasis rosea area and severity index. Cure was defined as the absence of erythema, with no or minimal scaling.

The number of days (mean ± standard deviation) taken for cure was not significantly different between the two groups (placebo 26.54 ± 9.14 days versus acyclovir 33.29 ± 9.49 days; P = 0.0720, t-test; 95% confidence interval of difference -0.65 to 14.14 days).

The sample size for the present study was calculated using data from an earlier study. As the standard deviation was not mentioned in that article, a common standard deviation of fifteen days was assumed. A study with a larger sample size may be more effective in detecting minor treatment differences between acyclovir and placebo, if they exist at all.

Acyclovir is not an effective treatment for pityriasis rosea.