Enhancement of enrofloxacin serum antibacterial activity by calcium primed broilers

The aim of this trial was to assess the effect that calcium gluconate priming of 468 broilers has on the antibacterial activity of a standard dose of enrofloxacin. Hence, a series of oral pharmacokinetic studies were carried out in four groups of broilers medicated individually through an oral cannula as follows: group A, medicated only with enrofloxacin 10 mg/kg; group B, receiving immediately one after the other, calcium gluconate (200 mg/kg) and enrofloxacin 10 mg/kg; group C, dosed first with calcium gluconate (200 mg/kg) and 1 h later enrofloxacin (10 mg/kg); and group D, dosed first with calcium gluconate (200 mg/kg) and 2 h later enrofloxacin (10 mg/kg). Broilers were bled at different times after the dose of enrofloxacin and antibacterial activity, measured as concentration of enrofloxacin, was measured by an agar diffusion assay. Results revealed that group D the greatest values of maximum serum concentration (Csmax), area under the concentration vs. time curve (AUC) and area under the moment curve (AUMC). These values were statistically higher than the corresponding ones derived from groups A, B and C (P < 0.05). Taking Csmax and AUC values of group A as reference baseline, an increase of 24% and 50%, respectively, was obtained in group D. Group B had the lowest Csmax, AUC, AUMC and elimination half life (T1/2β) and these values were statistically different from groups A, C and D (P < 0.05). The T1/2β was statistically longer in groups C and D as compared with A and B, and the former groups were also different between each other (P < 0.05). These results show that if calcium gluconate is first dosed to broilers and 2 h later enrofloxacin is administered (as in group D), a more pronounced antibacterial activity of enrofloxacin can be obtained. A challenge of this sequential dosing scheme in a field trial may reveal its clinical value.