Pharmacokinetics of rifampin given as a single oral dose in foals.

This study explores the pharmacokinetics of rifampin, an antibiotic medication, given as a single oral dose in foals aged 6 to 8 weeks. The results showed that the concentration of the drug in the foals’ bloodstream peaked at 4 hours after administration and gradually decreased over 24 hours.

Study Design and Methods

The research involved six foals aged between 6 to 8 weeks as study participants. Each of these foals was administered a single oral dose of rifampin. The dose administered was 10mg per kilogram of the foal’s body weight. The researchers took regular measurements of the levels of rifampin in the foals’ serum, a component of blood that contains proteins. These measurements were taken at different times over a 24-hour period.

• The foals were closely monitored and serum samples collected at several time points within the 24-hour duration post rifampin administration.
• The serum samples were then used to determine the concentration of rifampin present.

Findings

From the measurements taken, it was observed that the mean peak serum rifampin concentration was 6.7 micrograms per milliliter at about 4 hours following the treatment. This means that the highest concentration of the drug in the foals’ blood was found approximately 4 hours after the administration of the dose.

• After the peak concentrations, the serum levels of rifampin gradually declined over the next 20 hours as the antibiotic was metabolized and eliminated from the body.
• At the end of the monitoring period, which was 24 hours after the treatment had been administered, the serum concentration of rifampin had fallen to a mean value of 2.7 micrograms/ml indicating continued metabolism and clearance of the drug from the body.

Drug Clearance Data

The study also calculated the elimination half-life of rifampin in the foals, which was determined to be 17.5 hours. The term ‘elimination half-life’ refers to the time taken for the concentration of the drug to reduce to half its initial level.

• Additionally, the elimination rate constant for rifampin was measured at 0.04 per hour. The elimination rate constant is a pharmacokinetic parameter that correlates with the speed of drug clearance from the body.
• The slower the elimination rate constant, the longer the drug tends to stay within the body.

Overall, this study provides valuable information on how a single dose of rifampin is processed in the body of a young foal, influencing the interval between dosing in a clinical setting.