Pharmacokinetics of chloramphenicol in the neonatal horse.

This research explores the pharmacokinetics of the drug chloramphenicol in newborn horses. The study found that the drug is rapidly distributed and eliminated in the body, with the main characteristics not differing greatly from those seen in adult horses.

Methodology

• The research team gave chloramphenicol sodium succinate as an intravenous bolus with a dose of 50 mg/kg to eight foals.
• The foals weighed between 49-57 kg, with the average weight being 53.19 +/- 2.66 kg.
• The test foals were aged between 1 to 9 days, with the average age being 4.5 +/- 2.56 days.

Results of Intravenous Administration

• The drug was rapidly distributed throughout the body and followed first-order elimination, consistent with what’s typically found in pharmacokinetic studies.
• The mean pharmacokinetic values were as follows: zero-time serum concentration (the concentration of the drug in the blood immediately after administration) was 36.14 micrograms per milliliter; the apparent specific volume of distribution (the theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood) was 1.614 liters per kg; the elimination rate constant (the rate at which the drug is removed from the body) was 0.7295 per hour. This corresponds to a biological half-life (the time it takes for the body to eliminate half of the drug) of 0.95 hours.
• These results do not differ significantly from those reported for adult horses and ponies, suggesting that the drug behaves similarly in horses of different ages.

Methodology Variation

• The team also administered a suspension of chloramphenicol by nasogastric tube at 50 mg/kg to another group of seven foals.
• The weights of these foals also ranged from 49 to 57 kg, with an average weight of 51.34 +/- 2.82 kg.
• These test foals were aged from 1 to 7 days, with an average age being 4.43 +/- 1.90 days.

Results of Nasogastric Administration

• After administration, a mean peak serum chloramphenicol concentration of 23.97 micrograms per milliliter was reached 1.14 hours after administration.
• The bioavailability (the proportion of the drug that enters the circulation when introduced into the body and so is able to have an active effect) of this preparation was 83.27 percent.