Aqueous procaine penicillin G in the horse: serum, synovial, peritoneal, and urine concentrations after single-dose intramuscular administration.

This research article investigates the concentration of aqueous procaine penicillin G in the serum, synovial fluid, peritoneal fluid, and urine of six adult horses over a 48-hour period following a single-dose intramuscular administration.

Introduction and Methodology

• The study aims to understand the dispersal and concentration of procaine penicillin G in a horse’s body after a single dosage.
• Six adult female horses (mares) were chosen as the subjects of the study.
• Each horse was administered a single dose of procaine penicillin G, which is an antibiotic injection often used to treat bacterial infections. The dose was given intramuscularly (IM – into a muscle), at a dosage of 22,000 IU/kg of body weight, equivalent to 15.4 mg of penicillin G/kg.
• The concentration of penicillin in serum (blood), synovial fluid (fluid that helps in joint movements), peritoneal fluid (fluid in the abdominal cavity), and urine was measured over the next 48 hours. This was done at different time points to assess how the concentration changes over time.

Findings

• The researchers found that the average peak concentration of penicillin in the blood was 1.42 micrograms/ml. This peak was found at approximately 3 hours after the penicillin was administered.
• Penicillin was also found in the synovial and peritoneal fluids. The peak concentrations in these fluids were slightly lower, 0.62 micrograms/ml and 0.58 micrograms/ml, respectively. The synovial fluid reached its peak at 4 hours, while the peritoneal fluid reached its peak at 3 hours.
• All these concentrations decreased over time, in line with the decreasing concentrations in the serum. However, the concentration in each of these fluids was still measurable after 48 hours.
• The urine concentration of penicillin was higher than the others, with an average peak concentration of 525.81 micrograms/ml found at 8 hours. This peak suggests that penicillin is excreted in the urine, and the high concentration indicates this as a major pathway for the body to remove penicillin.

Conclusion

• This study provides valuable insight into the pharmacokinetics – the movement of drugs within the body – of procaine penicillin G in horses. The findings can be used to optimize dosage and administration time for effective treatment.