AZITHROMYCIN COMPARED WITH AMOXICILLIN IN THE TREATMENT OF ERYTHEMA MIGRANS - A DOUBLE-BLIND, RANDOMIZED, CONTROLLED TRIAL

Objective: To determine whether azithromycin or amoxicillin is more ef ficacious for the treatment of erythema migrans skin lesions, which ar e characteristic of Lyme disease. Design: Randomized, double-blind, do uble-dummy, multicenter study. Acute manifestations and sequelae were assessed using a standardized format. Baseline clinical characteristic s and response were correlated with serologic results. Patients were f ollowed for 180 days. Setting: 12 outpatient centers in eight states. Patients: 246 adult patients with erythema migrans lesions at least 5 cm in diameter were enrolled and were stratified by the presence of fl u-like symptoms (such as fever, chills, headache, malaise, fatigue, ar thralgias, and myalgias) before randomization. Intervention: Oral trea tment with either amoxicillin, 500 mg three times daily for 20 days, o r azithromycin, 500 mg once daily for 7 days. Patients who received az ithromycin also received a dummy placebo so that the dosing schedules were identical. Results: Of 217 evaluable patients, those treated with amoxicillin were significantly more likely than those treated with az ithromycin to achieve complete resolution of disease at day 20, the en d of therapy (88% compared with 76%; P = 0.024). More azithromycin rec ipients (16%) I than amoxicillin recipients (4%) had relapse (P = 0.00 5). A partial response at day 20 was highly predictive of relapse (27% of partial responders had relapse compared with 6% of complete respon ders; P < 0.001). For patients treated with azithromycin, development of an antibody response increased the possibility of achieving a compl ete response (81% of seropositive patients achieved a complete respons e compared with 60% of seronegative patients; P = 0.043). Patients wit h multiple erythema migrans lesions were more likely than patients wit h single erythema migrans lesions (P < 0.001) to have a positive antib ody titer at baseline (63% compared with 17% for IgM; 39% compared wit h 16% for IgG). Fifty-seven percent of patients who had relapse were s eronegative at the time of relapse. Conclusions: A 20-day course of am oxicillin was found to be an effective therapeutic regimen for erythem a migrans. Most patients were seronegative for Borrelia burgdorferi at the time of presentation with erythema migrans (65%) and at the time of relapse (57%).