Pharmacokinetics of the bovine formulation of enrofloxacin (Baytril 100) in horses.

The research investigated the pharmacokinetics of an injectable antibiotic formulation (Baytril 100) typically used for cattle, but being repurposed for equine treatment. Through the observation of six horses, the effectiveness of the formulation, administered both orally and intravenously at specific doses, was analyzed, particularly against organisms with a specific inhibitory concentration.

Introduction

• This study is essentially based on the pharmacokinetics of the bovine formulation of the antibiotic enrofloxacin (Baytril 100), previously approved for use in cattle, in horses.
• Despite the absence of pharmacokinetic data for horses, the antibiotic has gained popularity among equine practitioners, being administered orally and intravenously.

Methodology

• The methodology involved six healthy horses being given enrofloxacin in doses of 7.5 mg/kg both orally and intravenously.
• The sequence in which the drug was administered was randomly assigned and a gap of at least one week was maintained between administrations, to allow for any potential drug residues to clear out from the horse’s system (the washout period).
• From each horse, blood samples were collected at various intervals after drug administration to study the pharmacokinetic profile of this product.

Results

• Enrofloxacin, like other fluorinated quinolones, is an antimicrobial whose efficacy depends on its concentration. These drugs work best when the inhibitory quotient (a measure of the drug’s inhibitory effects) is at least 8.
• According to this study, when inhibitory quotients are between 8 and 10, once-daily administration of 7.5 mg/kg of the bovine injectable formulation of enrofloxacin (either orally or intravenously) indicates potential effectiveness against susceptible organisms.
• Such organisms are specifically those whose minimum inhibitory concentration for 90% of the isolates is lower than 0.5 microg/ml. In simple terms, these organisms are prone to be inhibited by the antibiotic when it is present in a concentration that is below this threshold.