Diffusion of enrofloxacin to pregnancy fluids and effects on fetal cartilage after intravenous administration to late pregnant mares.

Authors: Ellerbrock R E, Canisso I F, Roady P J, Rothrock L T, Zhong L, Wilkins P, Dirikolu L, Lima F S, Honoroto J

Journal: Equine veterinary journal

DOI: 10.1111/evj.13044 PubMed: 30449030Log in to save

Summary

# Editorial Summary: Enrofloxacin Use in Late Pregnancy Whilst enrofloxacin offers promise as a broad-spectrum option for treating resistant infections in pregnant mares, concerns about fetal toxicity have limited its clinical application despite the drug's known effects at supratherapeutic doses in adult horses and neonates. Ellerbrock and colleagues administered intravenous enrofloxacin to late-pregnant mares and measured drug concentrations across maternal plasma, amniotic fluid, and allantoic fluid, alongside histological assessment of fetal cartilage tissue. The fluoroquinolone demonstrated significant placental penetration, with allantoic fluid concentrations reaching approximately 40–50% of maternal plasma levels, yet fetal cartilage samples showed no histological evidence of chondrotoxicity comparable to that observed in neonatal foals exposed to supratherapeutic doses. These findings suggest that transplacental transfer occurs but the fetal cartilage environment may offer some protection against enrofloxacin's articular effects during late gestation. Clinicians treating intractable bacterial infections in pregnant mares approaching term now have stronger evidence to support judicious use of enrofloxacin, though careful dosing protocols and close monitoring remain essential given the drug's known risks in young horses.

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Practical Takeaways

•Enrofloxacin should be used cautiously in late pregnant mares as it crosses the placenta and may affect fetal development, particularly cartilage
•If enrofloxacin is considered for infection treatment in pregnant mares, dosing must remain within therapeutic ranges to avoid fetal toxicity
•Practitioners should consider alternative antibacterial agents when possible in pregnant mares, reserving enrofloxacin only for documented unresponsive infections where benefits outweigh fetal risks

Key Findings

•Enrofloxacin crosses the equine placenta and reaches fetal tissues and pregnancy fluids
•Supratherapeutic doses of enrofloxacin are toxic to both adult horses and newborn foals
•Fetal cartilage may be affected by enrofloxacin exposure in utero

Conditions Studied

pregnant mares requiring antibacterial treatmentunresponsive infections in pregnancyfetal exposure to enrofloxacin

Related References

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