Fluoroquinolone exposure in utero did not affect articular cartilage of resulting foals.

Summary

# Editorial Summary Fluoroquinolones such as enrofloxacin are known to cross the equine placenta, raising concerns about potential developmental toxicity despite the absence of obvious gross or histological damage in exposed fetuses. This 2021 study employed advanced biomechanical and microscopic analysis to investigate whether in utero fluoroquinolone exposure caused subtle cartilage defects that standard pathological examination might miss. Using high-resolution techniques beyond conventional histology, researchers found no evidence of articular cartilage damage in foals whose dams had received fluoroquinolone treatment during pregnancy, suggesting the drug's transplacental passage does not compromise joint tissue development. For equine practitioners, this provides reassurance that therapeutic use of these antimicrobials in pregnant mares—when clinically indicated—does not appear to compromise skeletal development through mechanisms detectable at the tissue level. However, the findings should not prompt complacency; continued judicious use and consideration of safer alternatives remain prudent practice, particularly given fluoroquinolones' known effects in other species and the ongoing need for long-term developmental follow-up studies.

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Key Findings

• •Fluoroquinolones (enrofloxacin and ciprofloxacin) cross the equine placenta without causing gross or histological lesions in fetuses or resulting foals
• •In utero fluoroquinolone exposure did not produce detectable adverse effects on articular cartilage development in foals

Conditions Studied

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