Disposition of penicillin G sodium following intravenous and oral administration to Equidae.

This research investigates how penicillin G sodium, a type of antibiotic, is absorbed and broken down in the bodies of horses, ponies, and donkeys after it has been given orally or intravenously. It was found that the antibiotic was broken down at similar rates in all three animals, but was not well-absorbed into the body when given orally.

Aim of the Study

• The aim of this research was to study and compare the plasma disposition (how the drug is distributed throughout the body) and the pharmacokinetics (how the body processes the drug) of penicillin G sodium in horses, ponies, and donkeys when administered intravenously.

Key Findings

• The half-life (time taken for the concentration of the drug to reduce by half in the body) of the antibiotic was found to be similar in all three animals – 39.0 minutes for horses, 27.3 minutes for ponies, and 31.5 minutes for donkeys.
• A dosage interval of 6-8 hours was suggested to be appropriate for infections caused by susceptible bacteria.
• The antibiotic was found to be absorbed quickly in the stomach, but the systemic availability (portion of the drug that enters the circulation after administration) was low (0.12% to 0.34%). This suggests that oral administration may not be effective for systemic antimicrobial therapy in these animals.
• A further study on two ponies with cannulated caecal fistulas (holes created surgically in the caecum, a pouch within the large intestine) was conducted. From this, it was observed that a low concentration of penicillin G (< or =0.6 micrograms ml-1) was found in the caecal fluid after injecting the drug intravenously. However, high concentrations (4.96-157.12 micrograms ml-1) were found after oral administration. This suggests a high risk of developing antimicrobial-associated colitis (inflammation of the large intestine), a side effect associated with the use of antimicrobials, after orally giving penicillin G.