A randomized, double-blind study to assess the optimal duration of doxycycline treatment for human brucellosis

Human brucellosis is usually treated with a combination of tetracyclines and aminoglycosides. However, the optimal duration of therapy has not been clearly determined.

We conducted a prospective, double-blind, randomized, multicenter study comparing treatment with doxycycline (100 mg po b.i.d.) for 30 days (30-day group) with the same dosage of doxycycline for 45 days (45-day group) in patients with brucellosis without endocarditis, spondylitis, or neurobrucellosis. All patients were treated with gentamicin (240 mg im once daily) for the first 7 days. Therapeutic outcome was evaluated by measuring relapse rates and drug safety.

Seventy-three patients were included in each group. During the first 45 days after treatment, the percentage of patients with relapse was significantly higher in the 30-day group than in the 45-day group (12.3% vs. 1.37%; relative risk, 9.00; 95% confidence interval [CI], 1.17-69.2; P=.017). Between day 45 after treatment and 12 months after treatment, no further significant differences were found in relapse rates between groups (9.38% in the 30-day group vs. 11.11% in the 45-day group; relative risk, 0.84; 95% CI, 0.31-2.30; P=.78). Overall, relapses occurred in 15 (20.55%) of 73 patients in the 30-day group and in 9 (12.33%) of 73 patients in the 45-day group (relative risk, 1.67; 95% CI, 0.78-3.56; P=.264). Compliance and adverse effects were comparable in the 2 groups.

Doxycycline treatment for 45 days significantly decreased early relapse rates among adults with brucellosis without increasing adverse effects.