PHARMACOKINETICS OF ENROFLOXACIN AFTER INTRAVENOUS, INTRAMUSCULAR ANDORAL-ADMINISTRATION IN HOUBARA BUSTARD (CHLAMYDOTIS-UNDULATA-MACQUEENII)

The in-vitro activity of enrofloxacin against 117 strains of bacteria isolated from bustards was determined. Minimum inhibitory concentratio ns for 72% of the Proteus spp., E. coli, Salmonella spp. and Klebsiell a spp. (n = 61) and for 48% of the Streptococci spp, and Staphylococci spp. (n = 31) were less than or equal to 0.5 mu g/mL. The minimum inh ibitory concentration (MIC) of 76% of Pseudomonas spp. (n = 25) was le ss than or equal to 2 mu g/mL. Fourteen strains were resistant to conc entrations greater than or equal to 128 mu g/mL. The elimination half- lives (t(1/2) elim beta) (mean +/- SEM) of 10 mg/kg enrofloxacin in ei ght houbara bustards (Chlamydotis undulata) were 6.80 +/- 0.79, 6.39 /- 1.49 and 5.63 +/- 0.54 h after oral (p.o.), intramuscular (i.m.) an d intravenous (i.v.) administration, respectively. Enrofloxacin was ra pidly absorbed from the bustard gastro-intestinal tract and maximum pl asma concentrations of 1.84 +/- 0.16 mu g/mL were achieved after 0.66 +/- 0.05 h. Maximum plasma concentration after i.m. administration of 10 mg/kg was 2.75 +/- 0.11 mu g/mL at 1.72 +/- 0.19 h. Maximum plasma concentration after i.m, administration of 15 mg/kg in two birds was 4 .86 mu g/mL. Bioavailability was 97.3 +/- 13.7% and 62.7 +/- 11.1% aft er i.m. and oral administration, respectively. Plasma concentrations o f enrofloxacin greater than or equal to 0.5 mu g/mL were maintained fo r at least 12 h for all routes at 10 mg/kg and for 24 h after i.m. adm inistration at 15 mg/kg. Plasma enrofloxacin concentrations were monit ored during the first 3 days of treatment in five houbara bustards and kori bustards (Ardeotis kori) with bacterial infections receiving a s ingle daily i.m. injection of 10 mg/kg for 3 days. The mean plasma enr ofloxacin concentrations in the clinical cases at: 27 and 51 h (3.69 a nd 3.86 mu g/mL) and at 48 h (0.70 mu g/mL) were significantly higher compared with the 3 h and 24 h time intervals from clinically normal b irds. The maximum plasma concentration (C-max)/MIC ratio was ranked i. v. (10/mg/kg) > i.m. (15 mg/kg) > i.m. (10 mg/kg) > oral (10 mg/kg), b ut it was only higher than 8:1 for i.v and i.m. administrations of enr ofloxacin at 10 mg/kg and 15 mg/kg, respectively, against a low MIC (0 .5 mu g/mL). A dosage regimen of 10 mg/kg repeated every 12 h, or 15 m g/kg repeated every 24 h, would be expected to give blood concentratio ns above 0.5 mu g/mL and hence provide therapeutic response in the bus tard against a wide range of bacterial infections.