Pharmacokinetics and body fluid and endometrial concentrations of cefoxitin in mares.

The research article is about a study conducted on four mares to ascertain the body fluid distribution and pharmacokinetics of Cefoxitin, an antibiotic commonly used for bacterial infections, after both intravenous and intramuscular administration.

Methodology

• Four healthy adult mares were administered a single dose of sodium Cefoxitin (20 mg/kg of body weight, IV) and then serum Cefoxitin concentrations were measured at intervals over a period of 6 hours.
• Values including, the mean elimination rate, elimination half-life, apparent volume of distribution (Vd) and clearance of the drug were calculated.
• This same set of mares along with an additional two were then given four intramuscular injections of sodium Cefoxitin (400 mg/ml) at a dosage of 20 mg/kg.
• Cefoxitin concentrations in serum, synovial fluid, peritoneal fluid, cerebrospinal fluid (CSF), urine, and endometrium were measured intermittently.

Results

• The mean elimination rate constant was found to be 1.08/hour and the elimination half-life was 0.82 hour.
• Apparent volume of distribution (Vd) was 0.12 L/kg and clearance was 259 ml/hr/kg.
• Peak serum concentration of 23.1 micrograms/ml was observed 30 minutes after the 2nd intramuscular injection.
• Peak concentration values were also calculated for synovial, peritoneal, and endometrial fluids.
• Cefoxitin concentration in urine was seen to be significantly high.

Implications and Conclusions

• Cefoxitin did not easily penetrate the CSF, implying its limited use in treating CNS infections.
• The bioavailability of Cefoxitin, when given intramuscularly, was calculated to be between 65% to 89%, with a mean of 77%, which indicates high absorption and systemic use.
• However, the study also reported an instance of one horse developing acute laminitis during the course of the study which hints at potential side effects.
• This research provides critical insights into the distribution, clearance, and bioavailability of Cefoxitin, particularly valuable for equine veterinary medicine.