Pharmacokinetics of marbofloxacin in horses.

This research investigates the pharmacokinetic properties of marbofloxacin, a fluoroquinolone antibiotic, in horses. The purpose of the study was to develop an optimal dosage regimen for horses to treat infections from certain bacteria. Findings indicate that a dose of 2 mg/kg/24h via different administrations was more effective for one type of bacteria compared to another.

Pharmacokinetics of Marbofloxacin in Horses

The research study focused on the pharmacokinetic properties of the fluoroquinolone antibiotic, marbofloxacin, when administered to horses. Pharmacokinetics refers to the body’s effect on a drug, encompassing the processes of absorption, distribution, metabolism, and excretion. Understanding these processes is crucial to determining the dosage of the drug.

• The research was conducted on six horses which received marbofloxacin via different administration routes – intravenous, subcutaneous, and oral.
• The administered dose was 2 mg/kg of the horse’s body weight.
• Parameters, like clearance and half-life of the drug, were studied. Clearance was found to be 0.25 l/kg/h and the half-life was a mean of 756 hrs.

Determination of Bioavailability

Bioavailability of a drug refers to the extent and rate at which it is absorbed into the body’s systemic circulation. The absolute bioavailability of marbofloxacin was determined:

• After subcutaneous administration, it was found to be 98% meaning that nearly all of the administered dose reached the bloodstream.
• On oral administration, the absolute bioavailability was 62%, indicating that around two-thirds of the administered dose reached the bloodstream.

Minimum Inhibitory Concentrations (MIC)

The MIC is the lowest concentration of an antimicrobial that will inhibit the visible growth of a microorganism after overnight incubation.

• The MIC required to inhibit 90% of enterobacteriaceae was found to be 0.027 microg/ml.
• For Staphylococcus aureus, a much higher concentration was needed – 0.21 microg/ml.

Choice of Dosage Regimen

Researchers then used this data to determine the optimal dosage regimen for treating bacterial infections. They simulated marbofloxacin concentration profiles and calculated surrogate markers of antimicrobial efficacy (like AUIC, Cmax/MIC ratio, and time above MIC90) for repeated administrations.

• Based on the pharmacokinetic properties and the bioavailability of marbofloxacin, a dose of 2 mg/kg of horse body weight every 24 hours was recommended.
• This regimen was found to be more effective for treating infections by enterobacteriaceae than for S. aureus, likely due to the lower MIC for the former.