Background: Doxycycline is widely used to treat Lyme disease associated with erythema migrans. Whether it is comparable to tetracycline is unknown.
Objective: We conducted a two-part retrospective analysis of (1) the safety and efficacy of doxycycline compared with tetracycline and (2) the safety and efficacy of a 14-day versus a 20-day course of doxycycline.
Methods: Twenty-seven patients given tetracycline (500 mg four times a day for 14 days [group 1]) were compared retrospectively with 21 patients who received doxycycline (100 mg two or three times a day for 14 days [group 2]). The results for group 2 were also compared with that of 38 patients who received doxycycline for 20 days (100 mg three times daily) in a prospective treatment trial (group 3).
Results: There was no significant difference in the incidence of adverse drug effects or in efficacy at 1 month, but at 1 year there was a trend toward a better outcome in the group treated with tetracycline (p = 0.08). A 14-day course of doxycycline was comparable to a 20-day course in the incidence of adverse drug effects and in clinical outcome.
Conclusion: The principal advantage of doxycycline over tetracycline for the treatment of Lyme disease associated with erythema migrans is the convenience of less frequent dosing, not enhanced efficacy or safety. There appears to be no advantage in extending treatment with doxycycline from 14 to 20 days.