Pharmacokinetics of sodium amoxicillin in foals after intramuscular administration.

The researchers investigated how a dose of sodium amoxicillin is metabolized in the bodies of foals at three different ages. They found that the process of absorption and elimination of the drug adjusts as the foals grow older, with notable changes in peak serum concentrations, elimination rate constants, and serum clearance rates.

Detailed Study Overview

• The objective of the study was to determine the pharmacokinetic values of sodium amoxicillin, a commonly used antibiotic, in foals at different stages of growth – specifically, at 3, 10, and 30 days old. This involved measuring how quickly the drug was absorbed, distributed, and eliminated from the body of the foals.
• To carry out the study, a single intramuscular injection of sodium amoxicillin was administered to six Quarter Horse foals at each of the targeted ages. Each dose was adjusted to the body weight of the foal – 22 milligrams for each kilogram of body weight.
• Serum amoxicillin concentrations were then recorded over a 24-hour period, to observe the patterns of absorption and elimination of the drug.

Key Findings

• The researchers found that the absorption of amoxicillin was fast, taking place 30 minutes post-injection, regardless of the foal’s age. The peak serum concentrations were 17.31 micrograms/ml at 3 days old, 23.28 micrograms/ml at 10 days old, and 21.35 micrograms/ml at 30 days old.
• Eight hours after administration, serum samples had amoxicillin concentrations of less than 0.05 micrograms/ml, indicating that the drug was rapidly eliminated from the body.
• With increasing age, there were noticeable changes in the elimination of the drug. The elimination rate constant, which measures how quickly a drug is removed from the body, increased as the foals aged. Similarly, serum clearance rates, that is the volume of plasma from which a substance is completely removed per unit time, also increased with age.
• In contrast, drug half-life, the time it takes for the concentration of the drug to drop to half its initial amount, decreased with age. However, the starting concentration of the drug and the apparent volume of distribution, which relates the amount of drug in the body to the concentration of the drug in the blood, did not change noticeably in the first 30 days of life.

Conclusion

• The study offered crucial insights into how the pharmacokinetics of sodium amoxicillin changes in foals during the initial 30 days of their lives. The varying elimination rate constants, serum clearance rates, and drug half-lives suggest the metabolic capability of foals changes as they age. These findings could be instrumental in adjusting the dosages and schedules of sodium amoxicillin, and potentially other drugs, in foals of different ages to ensure safe and effective treatment.