Pulmonary disposition and pharmacokinetics of a single oral dose of chloramphenicol in healthy fasted adult horses.

This research article investigates how different oral formulations of the drug chloramphenicol are absorbed and distributed in the bodies of horses, specifically focusing on the plasma and lungs. The study found that delivering this drug orally can achieve adequate concentrations in the lungs to potentially treat equine pneumonia.

Methods

• Six healthy adult horses belonging to the university were randomly chosen for the study.
• These animals received a single dose of chloramphenicol through either intravenous injection, oral administration in tablet form, or either orally or directly to the stomach in a compounded suspension formulation.
• Samples of blood plasma were taken at several points after treatment to trace the drug’s concentration over time.
• Bronchoalveolar lavage (BAL), a method for extracting the fluids present in the lungs, was conducted at 1, 4, and 8 hours post-administration to measure the drug’s concentration in the pulmonary epithelial lining fluid (PELF) and the collected cells (BALc).
• All concentrations were measured using a specific type of scientific instrument known as liquid chromatography-tandem mass spectrometry.

Results

• Regardless of the method and route of administration, concentrations of chloramphenicol were consistently higher in PELF than in plasma.
• The compounded suspension formulation delivered directly to the stomach produced higher maximum concentrations and overall drug exposure than when it was administered orally. The approximate bioavailability of the drug in this method was 79%.
• There were no significant differences in concentration between the compounded suspension and commercial tablet formulations when given orally.
• When given orally, such treatment maintained pulmonary concentrations of at least 2 and 4 µg/mL for a minimum of 4 hours (50-75% of a 6- to 8-hour dosing interval) in 4 out of the 5 horses treated.

Implications

• The findings suggest that oral administration of chloramphenicol can achieve sufficient pulmonary concentrations to potentially treat pneumonia in horses. Consequently, this can aid veterinarians to make informed decisions when targeting complex cases of equine pneumonia.