An Observational Study on the Pharmacokinetics of Levofloxacin in Lactating Atypical Pneumonia Patients

<b><i>Importance:</i></b> Atypical pneumonia in postpartum women may alter drug pharmacokinetics (PK) through cytokine-mediated changes in vascular permeability, yet the breast milk disposition of levofloxacin in this population remains uncharacterized. <b><i>Objective:</i></b> This observational study aimed to compare levofloxacin PK in lactating atypical pneumonia patients (<i>n</i> = 10) receiving 400 mg once daily for 3 days with historical healthy controls and to assess infant exposure risks. <b><i>Methods:</i></b> Breast milk samples from subjects 6-10 were collected at predetermined time points (0.5, 1, 2, 4, 6, 8, 10, 12, and 24 hours) following the last dose of 3 days. Subjects 1-5 had random daytime sampling. The concentration of levofloxacin in breast milk was measured using a validated high-performance liquid chromatography method with ultraviolet detection (correlation coefficient: 0.9997; limit of detection: 0.15 μg/mL; recovery: 91.36-102.28%; RSD <5%). PK parameters were derived using noncompartmental analysis in Phoenix WinNonlin (version 8.35). <b><i>Results:</i></b> Key milk PK parameters included C_max of subjects 1-5 was 15.74 ± 6.55 μg/mL, and in subjects 6-10 was 14.55 ± 2.56 μg/mL. The elimination half-life (t_1/2β) in subjects 1-5 was 7.46 ± 3.39 hours and in subjects 6-10 was 4.57 ± 1.14 hours. The AUC_0-24 in subjects 1-5 was 84.31 ± 22.60 mg·h/L and in subjects 6-10 was 63.99 ± 11.78 mg·h/L. <b><i>Conclusions:</i></b> Based on a 150 mL/kg/day milk intake, the estimated infant daily exposure in subjects 1-5 and 6-10 was 0.53 ± 0.14 and 0.40 ± 0.07 μg/kg/day, respectively, which was below 10% of the therapeutic dose (10 mg/kg once daily) for infants aged 0-12 months. This study first quantified levofloxacin in atypical pneumonia patients' breast milk using a validated method. Results suggest that breastfeeding can continue cautiously during maternal levofloxacin therapy. Avoid breastfeeding at peak drug concentration and monitor the infant for potential reactions.