Objective: To correlate the pharmacokinetics/pharmacodynamics (PK/PD) ratios of three pharmaceutical preparations of enrofloxacin with their clinical efficacy in treating BRD. Methods: The PK/PD ratios of three enrofloxacin preparations were determined in healthy calves. Then, 48 BRD-affected calves initially treated IV with 2.2 mg/kg of flunixinmeglumine, were randomly assigned to treatment with: enrofloxacin dihydrate-hydrochloride (enro-C) 10% water suspension daily (10 mg/kg subcutaneous for three to six days); enro-C with alginate (enro-C/Al), and reference enrofloxacin (enro-R), both intended for treatment every 72-h in two occasions (10 mg/kg). Results: The highest maximum plasma concentration (Cmax)/minimum inhibitory concentration (MIC) ratio was obtained with enro-C and the highest area under the curve (AUC) 0-72 /MIC ratio with enro-R, and enro-C/Al exhibited an AUC 0-72 /MIC smaller, but Cmax/ MIC higher than enro-R. Based on repeated statistical measurements, clinical progress revealed that the best outcomes were observed with enro-C (p < 0.05), and no statistical differences resulted by comparing enro-C/Al with enro-R. Conclusions and Relevance: If the priority in calves affected by BRD is to speed up their recovery, and despite the more significant amount of enro-C injected, using of lower doses of enrofloxacin as in the long-acting preparations is unsustainable. This study demonstrates that the clinical efficacy of enrofloxacin in cattle is optimally linked to Cmax/MIC rather than to AUC/MIC, which occurs better when injecting enro-C.

Objective: To correlate the pharmacokinetics/pharmacodynamics (PK/PD) ratios of three pharmaceutical preparations of enrofloxacin with their clinical efficacy in treating BRD. Methods: The PK/PD ratios of three enrofloxacin preparations were determined in healthy calves. Then, 48 BRD-affected calves initially treated IV with 2.2 mg/kg of flunixinmeglumine, were randomly assigned to treatment with: enrofloxacin dihydrate-hydrochloride (enro-C) 10% water suspension daily (10 mg/kg subcutaneous for three to six days); enro-C with alginate (enro-C/Al), and reference enrofloxacin (enro-R), both intended for treatment every 72-h in two occasions (10 mg/kg). Results: The highest maximum plasma concentration (Cmax)/minimum inhibitory concentration (MIC) ratio was obtained with enro-C and the highest area under the curve (AUC) 0-72 /MIC ratio with enro-R, and enro-C/Al exhibited an AUC 0-72 /MIC smaller, but Cmax/ MIC higher than enro-R. Based on repeated statistical measurements, clinical progress revealed that the best outcomes were observed with enro-C (p < 0.05), and no statistical differences resulted by comparing enro-C/Al with enro-R. Conclusions and Relevance: If the priority in calves affected by BRD is to speed up their recovery, and despite the more significant amount of enro-C injected, using of lower doses of enrofloxacin as in the long-acting preparations is unsustainable. This study demonstrates that the clinical efficacy of enrofloxacin in cattle is optimally linked to Cmax/MIC rather than to AUC/MIC, which occurs better when injecting enro-C.

Objective: To correlate the pharmacokinetics/pharmacodynamics (PK/PD) ratios of three pharmaceutical preparations of enrofloxacin with their clinical efficacy in treating BRD. Methods: The PK/PD ratios of three enrofloxacin preparations were determined in healthy calves. Then, 48 BRD-affected calves initially treated IV with 2.2 mg/kg of flunixinmeglumine, were randomly assigned to treatment with: enrofloxacin dihydrate-hydrochloride (enro-C) 10% water suspension daily (10 mg/kg subcutaneous for three to six days); enro-C with alginate (enro-C/Al), and reference enrofloxacin (enro-R), both intended for treatment every 72-h in two occasions (10 mg/kg). Results: The highest maximum plasma concentration (Cmax)/minimum inhibitory concentration (MIC) ratio was obtained with enro-C and the highest area under the curve (AUC) 0-72 /MIC ratio with enro-R, and enro-C/Al exhibited an AUC 0-72 /MIC smaller, but Cmax/ MIC higher than enro-R. Based on repeated statistical measurements, clinical progress revealed that the best outcomes were observed with enro-C (p < 0.05), and no statistical differences resulted by comparing enro-C/Al with enro-R. Conclusions and Relevance: If the priority in calves affected by BRD is to speed up their recovery, and despite the more significant amount of enro-C injected, using of lower doses of enrofloxacin as in the long-acting preparations is unsustainable. This study demonstrates that the clinical efficacy of enrofloxacin in cattle is optimally linked to Cmax/MIC rather than to AUC/MIC, which occurs better when injecting enro-C.

Objective: To correlate the pharmacokinetics/pharmacodynamics (PK/PD) ratios of three pharmaceutical preparations of enrofloxacin with their clinical efficacy in treating BRD. Methods: The PK/PD ratios of three enrofloxacin preparations were determined in healthy calves. Then, 48 BRD-affected calves initially treated IV with 2.2 mg/kg of flunixinmeglumine, were randomly assigned to treatment with: enrofloxacin dihydrate-hydrochloride (enro-C) 10% water suspension daily (10 mg/kg subcutaneous for three to six days); enro-C with alginate (enro-C/Al), and reference enrofloxacin (enro-R), both intended for treatment every 72-h in two occasions (10 mg/kg). Results: The highest maximum plasma concentration (Cmax)/minimum inhibitory concentration (MIC) ratio was obtained with enro-C and the highest area under the curve (AUC) 0-72 /MIC ratio with enro-R, and enro-C/Al exhibited an AUC 0-72 /MIC smaller, but Cmax/ MIC higher than enro-R. Based on repeated statistical measurements, clinical progress revealed that the best outcomes were observed with enro-C (p < 0.05), and no statistical differences resulted by comparing enro-C/Al with enro-R. Conclusions and Relevance: If the priority in calves affected by BRD is to speed up their recovery, and despite the more significant amount of enro-C injected, using of lower doses of enrofloxacin as in the long-acting preparations is unsustainable. This study demonstrates that the clinical efficacy of enrofloxacin in cattle is optimally linked to Cmax/MIC rather than to AUC/MIC, which occurs better when injecting enro-C.