Pharmacokinetic profile of sulphamonomethoxine-trimethoprim in horses after intravenous, intramuscular and oral administration.

The research article focuses on a study that explores the pharmacokinetic profile of a sulphamonomethoxine-trimethoprim (SMM-TMP) combination in horses when administered in three different ways – intravenously, intramuscularly, and orally.

Objective and Methodology

• The main aim of the study was to investigate the pharmacokinetic profile of a drug combination – Sulphamonomethoxine (SMM), a sulphonamide antimicrobial drug normally used in veterinary practice, and Trimethoprim (TMP), an antibiotic useful for the treatment of a wide variety of bacterial infections.
• The combination was administered to a sample of five horses through three different routes, namely, intravenous, intramuscular, and oral routes.
• The dose of the administered combination remained consistent at 20 mg of SMM and 4 mg of TMP for each kilogram of bodyweight.

Key Findings

• The results of the study showed that after intravenous administration, both drugs dispersed rapidly, with SMM showing a distribution half-life of about 12 minutes and TMP about 18 minutes.
• The elimination half-life, i.e., the time taken for the concentration of a drug in the body to reduce by half, showed uniformity across all three administration routes. This indicated that the route of administration didn’t affect the elimination process.
• The bioavailability of the drug was high when it was administered in an aqueous solution by both intramuscular and oral routes. For SMM, it was approximately 72% when injected and 84% when orally administered. For TMP, the bioavailability was estimated to be about 84% and 98% for intramuscular and oral administrations, respectively.

Conclusion of the Study

• The study concludes by suggesting that administering the SMM-TMP orally once daily at the dosage of 20 mg and 4 mg per kg of bodyweight is suitable for maintaining therapeutic concentrations in horses.
• However, for treating systemic infections, administering the same twice daily in an intramuscular way would be more effective than the once-daily regimen usually adopted in veterinary practice.