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Journal Of General Internal Medicine

The risk of developing Lyme disease after a bite by a deer tick is small, estimated at only 1.0 to 3.5 percent. Some studies have demonstrated an advantage, although not statistically significant, in using antibiotics to treat patients with tick bite as a means of preventing development of Lyme disease. Warshafsky and colleagues conducted a meta-analysis to determine if the risk of Lyme disease is lower in patients who received prophylactic treatment with antibiotics after an Ixodes tick bite.

A MEDLINE search for English-language articles was performed. Trials that enrolled patients who received treatment or placebo within 72 hours of the tick bite, yet who had no evidence of Lyme disease at the time of entering the study, were included in the analysis. Demographic information, antibiotics used and duration of therapy and follow-up were assessed. Symptoms and/or signs consistent with Lyme disease (e.g., erythema migrans, seventh cranial nerve palsy, arthritis) were also reviewed.

Three studies were included in the final analysis. Overall, 600 patients (adults and children) were included in the studies, with 308 receiving treatment and 292 receiving placebo. Follow-up periods in the studies ranged from six months to three years. The antibiotics used in the studies were amoxicillin, penicillin or tetracycline, depending on the trial and the age of the patient. No serious side effects were reported in any of the studies, although rash developed in a small proportion of patients (1 to 4 percent) who received amoxicillin or penicillin.

Lyme disease did not develop in any of the patients who received antibiotic prophylaxis, whereas the disease developed in 1.1 to 3.4 percent of patients who received placebo. Although the odds ratio for prophylaxis was zero, the difference in risk between treated groups and placebo groups was not statistically significant. In addition, none of the patients in the placebo group subsequently had serious sequelae of Lyme disease.

The authors maintain that, even in endemic areas, the evidence does not support the routine use of antibiotic prophylaxis in patients with Ixodes tick bites. They calculate that one case of Lyme disease may be prevented for every 83 patients treated with antibiotics, but that the risks of antibiotic use (even minor side effects) outweigh the benefits of attempted prevention.

Warshapsky S, et al. Efficacy of antibiotic prophylaxis for prevention of Lyme disease. J Gen Intern Med 1996;11:329-33.

COPYRIGHT 1996 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group