Effect of long-term administration of an injectable enrofloxacin solution on physical and musculoskeletal variables in adult horses.
OBJECTIVE
To evaluate clinical safety of administration of injectable enrofloxacin.


METHODS
Randomized controlled clinical trial.


METHODS
24 adult horses.


METHODS
Healthy horses were randomly allocated into 4 equal groups that received placebo injections (control) or IV administration of enrofloxacin (5 mg/kg [2.3 mg/lb], 15 mg/kg [6.8 mg/lb], or 25 mg/kg [11.4 mg/lb] of body weight, q 24 h) for 21 days. Joint angles, cross-sectional area of superficial and deep digital flexor and calcaneal tendons, carpal or tarsal osteophytes or lucency, and midcarpal and tarsocrural articular cartilage lesions were measured. Physical and lameness examinations were performed daily. Measurements were repeated after day 21, and articular cartilage and bone biopsy specimens were examined.


RESULTS
Enrofloxacin did not induce changes in most variables during administration or for 7 days after administration. One horse (dosage, 15 mg/kg) developed lameness and cellulitis around the tarsal plantar ligament during the last week of administration. One horse (dosage, 15 mg/kg) developed mild superficial digital flexor tendinitis, and 1 horse (dosage, 25 mg/kg) developed tarsal sheath effusion without lameness 3 days after the last administration. High doses of enrofloxacin (15 and 25 mg/kg) administered by bolus injection intermittently induced transient neurologic signs that completely resolved within 10 minutes without long-term effects. Slower injection and dilution of the dose ameliorated the neurologic signs. Adverse reactions were not detected with a 5 mg/kg dose administered IV as a bolus.


CONCLUSIONS
Enrofloxacin administered IV once daily at the rate of 5 mg/kg for 3 weeks is safe in adult horses.
Bertone
A L
AL
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus 43210, USA.
Tremaine
W H
WH
Macoris
D G
DG
Simmons
E J
EJ
Ewert
K M
KM
Herr
L G
LG
Weisbrode
S E
SE
D000818:Animals; D000890:Anti-Infective Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D001706:Biopsy / Q000662:veterinary; D001772:Blood Cell Count; D001774:Blood Chemical Analysis; D001842:Bone and Bones / Q000473:pathology; D002358:Cartilage, Articular / Q000473:pathology; D000077422:Enrofloxacin; D005069:Evaluation Studies as Topic; D005260:Female; D024841:Fluoroquinolones; D006736:Horses / Q000502:physiology*; D007267:Injections / Q000662:veterinary; D007596:Joints / Q000000981:diagnostic imaging / Q000502:physiology; D007794:Lameness, Animal; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects*; D015363:Quinolones / Q000008:administration & dosage / Q000009:adverse effects / Q000494:pharmacology*; D011859:Radiography / Q000662:veterinary; D014463:Ultrasonography
D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D015363:Quinolones; D000077422:Enrofloxacin