Administration of enrofloxacin during late pregnancy failed to induce lesions in the resulting newborn foals.
Authors: Ellerbrock R E, Canisso I F, Roady P J, Litsky A, Durgam S, Podico G, Li Z, Lima F S
Journal: Equine veterinary journal
Summary
# Editorial Summary: Enrofloxacin Safety in Late Pregnancy Concerns about fluoroquinolone-induced cartilage and tendon damage in foals have limited their clinical use during pregnancy, yet evidence for this risk remains sparse. Ellerbrock and colleagues investigated whether enrofloxacin administered to mares in late gestation (day 280) would compromise musculoskeletal development by treating pregnant mares with either therapeutic (7.5 mg/kg) or double-dose (15 mg/kg) enrofloxacin for 14 days, then examining their foals' cartilage and tendons macroscopically and histologically at five weeks of age, whilst also performing biomechanical testing to failure on foal tendons. Neither treatment protocol produced visible lesions, clinical lameness, or differences in tendon tensile strength compared to untreated controls, though osteochondral changes appeared equally in both treatment and control groups—a finding unrelated to in utero fluoroquinolone exposure. The results suggest that short-term enrofloxacin use during late pregnancy poses minimal risk to foal musculoskeletal integrity within the first five weeks of life; however, the study's single gestational timepoint, reliance on healthy mares only, and assessment window of just five weeks leave critical questions unanswered about earlier gestation exposure, longer-term developmental effects through the first year, and whether more sensitive imaging techniques might detect subclinical changes. Until further investigation clarifies safety across all gestation stages and into yearling age, clinicians should continue weighing the antimicrobial benefits of fluoroquinolones against theoretical risks when treating pregnant mares with systemic infections.
Read the full abstract on PubMed
Practical Takeaways
- •Enrofloxacin use in late-pregnant mares (280+ days gestation) at recommended therapeutic doses appears safe in the short term, with no cartilage, tendon, or clinical lameness issues observed in foals by 5 weeks old
- •Further long-term studies are needed as this research only evaluated foals to 5 weeks of age and did not assess treatment at earlier gestational stages
- •Current findings do not support avoiding enrofloxacin in late gestation based on fear of cartilage or tendon damage to the fetus, though practitioners should remain cautious pending longer-term outcome data
Key Findings
- •Enrofloxacin administration at therapeutic (7.5 mg/kg) and supratherapeutic (15 mg/kg) doses during late gestation (280 days) did not induce macroscopic or microscopic cartilage lesions in foals by 5 weeks of age
- •No significant difference in tendon tensile strength was found between foals exposed to enrofloxacin in utero and control foals at 5 weeks of age
- •Osteochondral changes were present in both treatment and control foals with no apparent association with fluoroquinolone exposure during pregnancy
- •No clinical lameness was observed in any foal through 5 weeks of age regardless of maternal enrofloxacin treatment