Chloramphenicol and the neonatal calf.

Area of Science:

• Veterinary Pharmacology
• Neonatal Animal Physiology
• Toxicology

Background:

• Chloramphenicol is a broad-spectrum antibiotic with potential toxicity concerns.
• Neonatal animals often exhibit altered drug metabolism and elimination compared to adults.
• Understanding chloramphenicol pharmacokinetics in newborn calves is crucial for safe and effective use.

Purpose of the Study:

• To determine pharmacokinetic values of chloramphenicol in newborn calves.
• To assess potential toxic effects of chloramphenicol on bone marrow and hematologic values.
• To compare chloramphenicol elimination rates with antipyrine and evaluate different administration routes.

Main Methods:

• Chloramphenicol administered intravenously (IV) weekly or every 12 hours to newborn calves.
• Intramuscular (IM) and subcutaneous routes tested in older calves.
• Pharmacokinetic parameters, elimination rates, and toxicological markers (bone marrow, hematology, serum chemistry) analyzed.

Main Results:

• Elimination half-lives for chloramphenicol and antipyrine were significantly increased in newborn calves (first 3-4 weeks).
• Apparent bioavailability of chloramphenicol was 50%-60% via IM and subcutaneous routes in older calves.
• High and prolonged serum chloramphenicol concentrations did not induce significant toxic effects; bone marrow and hematologic values remained normal.

Conclusions:

• Newborn calves exhibit delayed chloramphenicol elimination, leading to prolonged high serum concentrations.
• Despite prolonged exposure, chloramphenicol showed minimal toxicity in the bone marrow and hematologic parameters of newborn calves.
• These findings suggest a potentially wider safety margin for chloramphenicol in neonatal calves than previously assumed.