Azithromycin gel fails to prevent Lyme disease
In a recent study conducted in Germany and Austria, researchers applied a 10% azithromycin gel to the site of a tick bite for 3 days. The trial was stopped early after it failed to prove that the gel worked in preventing Lyme disease (LD) for the 995 subjects. The topical treatment failed to prevent a combination of seroconversion or an EM rash in 11 (2%) of 505 individuals in the azithromycin group and 11 (2%) of 490 participants in the placebo group.
by Daniel J. Cameron, MD MPH
The findings of this double-blinded placebo controlled clinical trial were published in The Lancet Infectious Disease. In a post hoc analysis of 134 subjects, the authors were able to prevent 6 rashes if the gel was applied after a tick bite. The gel delayed the onset of EM rashes by 33 and 51 days, respectively, in an additional two subjects.
The trial did not show that the 10% azithromycin gel could prevent Lyme disease. It only demonstrated that the gel could prevent or delay a few EM rashes in a subset of patients bitten by a tick.
It would be nice to have a quick fix to prevent Lyme disease following a tick bite. But treatment with azithromycin gel is not the answer. Based on this trial, the gel should not be used to prevent Lyme disease.
- Schwameis, M., et al., Topical azithromycin for the prevention of Lyme borreliosis: a randomised, placebo-controlled, phase 3 efficacy trial. Lancet Infect Dis, 2016.