OBJECTIVE: To determine the efficacy of azithromycin in the treatment of patients with typical cat scratch disease (CSD).

DESIGN: Prospective, randomized, double-blind, placebo-controlled clinical trial.

SETTING: Large military medical center and its referring clinics.

PATIENTS: Active duty military members and their dependents with laboratory confirmed, clinically typical CSD.

INTERVENTION: Study participants assigned by randomization to treatment with oral azithromycin or placebo for five days.

OUTCOME MEASURES: Lymph node volume was calculated using three-dimensional ultrasonography (US) at entry and at weekly intervals. The ultrasonographer was blinded to the treatment groups. End-point evaluations were predetermined as time in days to 80% resolution of the initial total lymph node volume.

RESULTS: Demographic and clinical data showed that the azithromycin and placebo treatment groups were comparable at entry although the placebo group tended to be older. Eighty percent decrease of initial lymph node volume was documented in 7/14 azithromycin treated patients compared to 1/15 placebo treated controls during the first 30 days of observation (P = 0.026). After 30 days there was no significant difference in rate or degree of resolution between the two groups.

CONCLUSION: Treatment of patients with typical CSD with oral azithromycin for five days affords significant clinical benefit as measured by total decrease in lymph node volume within the first month of treatment.