Diffusion of enrofloxacin to pregnancy fluids and effects on fetal cartilage after intravenous administration to late pregnant mares
Ellerbrock, R. E., Canisso, I. F., Roady, P. J., Rothrock, L. T., Zhong, L., Wilkins, P., Dirikolu, L., Lima, F. S., Honoroto, J.
This study investigated the concentration of enrofloxacin and ciprofloxacin in pregnancy fluids when administered during late‐term pregnancy, in addition to assessing the effect on fetal articular cartilage.
Sixteen healthy pregnant mares at 260 days gestation were randomly allocated into one of three groups: control (no treatment; n = 3), enrofloxacin 5 mg/kg bwt i.v. (recommended therapeutic dose; n = 7) and enrofloxacin 10 mg/kg bwt i.v. (supratherapeutic dose; n = 6). Enrofloxacin was administered s.i.d. for 11 days. Amniotic and allantoic fluid were sampled on days 1, 5 and 11, and blood samples obtained daily.
On day 11 abortion was induced by manual cervical dilation and the fetuses euthanased following delivery. Fetal articular cartilage was examined macroscopically and histologically for lesions. Concentrations of enrofloxacin and ciprofloxacin in samples were measured by liquid chromatography-tandem mass spectrometry.
Enrofloxacin and ciprofloxacin reached fetal circulation and accumulated in the pregnancy fluids, reaching the minimum inhibitory concentrations for common pathogens in all fluids. No differences were seen in fetal serum biochemistry values between the control and treatment groups. No lesions were noted on gross inspection of any fetal articular surface and no major abnormal findings were observed on histological evaluation.
Bottom line: Enrofloxacin and ciprofloxacin are detectable in the fetus and fetal fluids after administration to late‐term mares but did not result in detectable effects on foal cartilage.