Correlation between Serum Doxycycline Concentrations and Serologic Evolution in Patients with Coxiella burnetii Endocarditis

Abstract

The recommended treatment for Q fever endocarditis is a combination of doxycycline and hydroxychloroquine. We found a correlation between serum doxycycline concentrations and decreases in levels of phase 1 Coxiella burnetii antibodies, in 24 patients with Q fever endocarditis. Patients who had a >2-fold decrease in levels of phase 1 antibodies had serum doxycycline concentrations higher than those of the other patients (mean ± SD, 5.29 ± 1.75 vs. 3.14 ± 1.40 μg/mL; P = .003). We recommend adjusting the posology of doxycycline to achieve a serum concentration of at least 5 μg/mL.