Pharmacokinetics of trimethoprim-sulphamethoxazole in two-day-old foals after a single intravenous injection.

This research article studies the effects of trimethoprim-sulphamethoxazole, a common antibiotic, in two-day-old foals. Researchers administered a single intravenous injection of this drug and monitored its concentration in the foals’ serum over a 24-hour period to determine how it’s metabolized and how it may aid in treating infections, particularly those caused by gram-positive bacteria.

Study Design

• The study included six healthy two-day-old foals, with three foals each from pony and horse categories.
• The researchers administered a single intravenous (IV) dose of trimethoprim (TMP)-sulphamethoxazole (SMZ) to each foal.
• This dosage was 2.5 mg of TMP and 12.5 mg of SMZ per kilogram of the foal’s bodyweight.
• After the injection, the serum TMP and SMZ concentrations were measured at multiple intervals during a 24-hour period.

Results and Findings

• The rate at which TMP was eliminated from the body (known as the elimination rate constant, or K) was the same in both pony and horse foals, measured at 0.45/hour.
• However, the K value for SMZ varied between pony and horse foals, at 0.12/hour and 0.07/hour respectively.
• The difference in the K values for SMZ was not significantly different, statistically speaking (P > 0.05).
• Based on previously published data regarding the minimum inhibitory concentration of TMP/SMZ against common characteristics of equine pathogens, it suggests the primary use of TMP/SMZ could be for treating infections caused by gram-positive bacteria.

Recommendations

• The researchers suggest a dosage of 2.5 mg of TMP and 12.5 mg of SMZ per kilogram of foal bodyweight, given via IV at 12-hour intervals, would be appropriate for treatment.

Conclusion

• This research offers vital ideas about TMP/SMZ usage in the medical treatment of young foals, especially against infections caused by gram-positive bacteria. Though some differences were noted in drug metabolism, the overall treatment approach appears effective.