Characterization of the penetration of garenoxacin into the breast milk of lactating women.

The primary objective of this study was to characterize the extent of excretion of garenoxacin, a novel des-F(6)-quinolone antimicrobial, into the breast milk of lactating women. A secondary objective was to determine the time after dose administration that garenoxacin was no longer detected in breast milk so as to define when a mother may resume breastfeeding if it was interrupted for garenoxacin administration. Six healthy, lactating women (age [mean +/- SD]: 32 +/- 6 years; weight: 68.3 +/- 19.8 kg; body mass index: 26 +/- 5 kg/m(2)) who had completed weaning their infants were administered a single 600-mg oral dose of garenoxacin. Plasma samples were collected predose and repeatedly up to 72 hours postdose. Breast milk was collected predose and for 6- to 12-hour intervals repeatedly up to 120 hours postdose. Breast milk/plasma concentration ratios for garenoxacin ranged from 0.35 to 0.44 up to 24 hours postdose, and the mean peak breast milk concentration was 3.0 microg/mL (0- to 6-h collection interval). Overall, garenoxacin exposure in breast milk was minimal, with a mean of 0.07% of the administered dose recovered within 120 hours. Indeed, garenoxacin was undetectable in the breast milk of a majority of subjects within 84 hours of dosing. As such, an infant nursing from a mother who had received a single 600-mg oral dose of garenoxacin could theoretically be exposed to 0.42 mg of garenoxacin (0.105 mg/kg/day for a 4-kg infant over the period of 5 days of nursing). If extrapolated to a 14-day course of garenoxacin 600 mg once daily, total exposure would be approximately 5.88 mg. These findings indicate that, like other quinolone antimicrobials, garenoxacin is secreted in breast milk.