Ocular penetration of intravenously administered enrofloxacin in the horse.
BACKGROUND
Information on antibiotic concentrations in the equine eye following systemic therapy is limited. Reports that Leptospira spp. are frequently present in the eyes of horses with recurrent uveitis, emphasises a need for studies on ocular concentrations of specific antibiotics.


OBJECTIVE
1) Enrofloxacin, administered i.v. at 7.5 mg/kg bwt q. 24 h, results in aqueous humour concentrations greater than the reported minimum inhibitory concentration (MIC) for Leptospira pomona. 2) Aqueous humour paracentesis sufficiently disrupts the blood-aqueous humour barrier (BAB) to cause an increase in aqueous humour protein and enrofloxacin concentrations.


METHODS
Aqueous humour enrofloxacin and total protein concentrations were determined in 6 healthy, mature horses after i.v. administration of enrofloxacin. Paracentesis was performed on the left eye on Days 3 and 4, 1 h following enrofloxacin administration, to determine enrofloxacin concentrations in healthy eyes and in eyes with mechanical disruption of the BAB. Paracentesis was also performed on the right eye 23 h after enrofloxacin administration. Blood samples were collected from the horses at identical times to determine enrofloxacin aqueous humour:plasma ratios.


RESULTS
Mean +/- s.d. enrofloxacin concentration in the aqueous humour 1 h post administration on Day 3 was 0.32 +/- 0.10 mg/l (range 0.18-0.47); and aqueous humour enrofloxacin, total protein and aqueous humour:plasma enrofloxacin ratios were higher on Day 4 than Day 3.


CONCLUSIONS
Following disruption of the BAB, enrofloxacin concentrations were above the reported MIC for Leptospira pomona.
Divers
T J
TJ
Department of Clinical Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
Irby
N L
NL
Mohammed
H O
HO
Schwark
W S
WS
D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D001082:Aqueous Humor / Q000737:chemistry; D019540:Area Under Curve; D018916:Blood-Aqueous Barrier; D000077422:Enrofloxacin; D024841:Fluoroquinolones / Q000493:pharmacokinetics*; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007275:Injections, Intravenous / Q000662:veterinary; D007919:Leptospira / Q000187:drug effects; D007922:Leptospirosis / Q000188:drug therapy / Q000662:veterinary*; D019152:Paracentesis / Q000662:veterinary; D016896:Treatment Outcome; D014605:Uveitis / Q000188:drug therapy / Q000662:veterinary*
D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D000077422:Enrofloxacin