Erythema migrans
Oral antibiotic therapy shortens the duration of the rash and generally prevents development of late sequelae. Among the 3 drugs used for this indication, only doxycycline is also effective against A. phagocytophilum infection; it should not be used in pregnant women or children less than eight years old. One double-blind controlled trial in 180 patients with erythema migrans showed that 10 days treatment with doxycycline was as effective as 20 days. Some patients remained symptomatic at the end of antibiotic therapy, but they continued to improve after treatment at the same rate regardless of whether they were treated for 10 or 20 days. One patient in the 10-day group developed meningitis.
Amoxicillin is as effective as doxycycline and is preferred for children less than 8 years old and pregnant or lactating women. Cefuroxime axetil (Ceftin) is also effective, but much more costly.