Effect of long-term administration of an injectable enrofloxacin solution on physical and musculoskeletal variables in adult horses.

This study assesses the clinical safety of long-term usage of injectable enrofloxacin, an antibiotic, in adult horses. The researchers conducted randomized controlled clinical trials with 24 horses and concluded that administering enrofloxacin intravenously at a rate of 5 mg/kg once daily for 3 weeks is safe for adult horses.

Research Method

• The researchers enrolled 24 healthy adult horses in this randomized controlled clinical trial.
• The horses were randomly divided into four equal groups. One group received a placebo, while the other three were given different doses of IV enrofloxacin (5mg/kg, 15mg/kg, or 25mg/kg of body weight once every 24 hours) for 21 days.
• Several physical and musculoskeletal variables were monitored, including joint angles, cross-sectional areas of tendons, the presence of osteophytes or articular cartilage lesions, and daily physical and lameness examinations.
• Measurements were repeated on day 21, and articular cartilage and bone biopsy specimens were examined.

Results

• Overall, enrofloxacin did not induce changes in most of the evaluated variables either during administration or for 7 days after administration.
• However, at higher doses (15 and 25 mg/kg), some adverse effects were observed. One horse developed lameness and cellulitis around the tarsal plantar ligament, and another showed signs of mild superficial digital flexor tendinitis. Another horse developed tarsal sheath effusion without lameness three days after the last administration.
• Interestingly, high doses of enrofloxacin given intermittently caused transient neurologic signs, which resolved completely within 10 minutes and had no long-term effects. These signs were mitigated by slower injection and dilution of the dose.
• No adverse reactions were detected when using a 5 mg/kg dose administered intravenously as a single injection.

Conclusions

• In conclusion, the study determined that IV administration of enrofloxacin at a dose of 5 mg/kg once daily for 21 days is safe in adult horses.
• Higher doses showed some negative effects and thus should be administered with caution, especially considering the temporary neurologic signs noted with bolus injection.