Pharmacokinetic/pharmacodynamic analysis of cephalothin after intramuscular administration in Thoroughbred horses.

This research article investigates the most effective dosage schedule of cephalothin, a type of antibiotic, when administered intramuscularly to Thoroughbred horses. Using a mathematical modelling approach, the study found that a dosage of 11 mg/kg every 8 or 6 hours provided 90% probability of successfully treating S. zooepidemicus and S. aureus infections.

Study Design

• The study employs a pharmacokinetic/pharmacodynamic (PK/PD) approach. This involves studying the rate at which a drug is processed in the body (pharmacokinetics) and the effects it has on the body (pharmacodynamics).
• The PK/PD model was applied to cephalothin (CET), an antibiotic, to find an effective dosage regimen when given by intramuscular (IM) injection.
• The research involved a sample size of eight Thoroughbred horses, each given a single IM dose of CET at 11 mg/kg body weight.

Methodology and Results

• The researchers measured CET plasma concentrations in the horses after the drug was administered.
• The measurements were processed using a nonlinear mixed-effect model, a statistical tool used in drug testing to account for variability between different subjects.
• The probability of target attainment (PTA) was calculated. This is basically the likelihood that the drug treatment will reach the intended effect.
• Using a Monte Carlo simulation, a computational technique that generates random sampling outcomes, the PTA was calculated for 5,000 horses.
• The study found that administering CET via IM injection at 11 mg/kg body weight every 8 hours and every 6 hours achieved a PTA of 90% in treating S. zooepidemicus and S. aureus infections, respectively.

Implications of the Findings

• This suggests these are effective dosage regimens for treating these types of infections in horses.
• The research also indicated that the total dose suggested for IM administration in this study was lower than that recommended for intravenous (IV) administration in previous studies.
• This research could potentially have an impact on horse health management, optimization of drug treatments, and could contribute to more cost-effective use of antibiotics.