Pharmacokinetics in pulmonary epithelial lining fluid and plasma of ampicillin and pivampicillin administered to horses.

This study examines how the drug ampicillin disperses in the lung lining fluid and blood plasma of horses, and how this may affect its effectiveness in treating common respiratory infections. The work reveals that the drug is well absorbed when given orally, and has a notable presence in lung fluid up to 12 hours after administration.

Research Objectives

• The primary objective of this study was to explore the concentrations of the antibiotic ampicillin in pulmonary epithelial lining fluid (PELF) and plasma of horses, after it was administered either directly (intravenous injection) or indirectly as a prodrug (pivampicillin) via gastric administration.
• This study also sought to relate the achieved ampicillin concentrations to the minimum inhibitory concentrations (MIC) of common pathogens causing respiratory infections in horses.

Methods and Findings

• Ampicillin was either directly injected (15mg/kg) or a prodrug pivampicillin (19.9mg/kg) was given orally.
• The results showed that ampicillin is quickly eliminated from the body, with it not being detectable in plasma just 12 hours after intravenous administration in half of the horses tested.
• Pivampicillin, on the other hand, was found to be well-absorbed in non-fasting horses and had an oral bioavailability of 36%.
• The degree of penetration of ampicillin into PELF, was 0.40 after intravenous administration and 1.00 after pivampicillin administration, indicating a higher concentration in PELF when pivampicillin was orally administered.

Conclusion and Clinical Relevance

• The study concludes that ampicillin, when administered either through an intravenous injection or orally as pivampicillin, can provide clinically relevant concentrations in the lung fluid for up to 12 hours.
• This raises the possibility that it could be effective in treating respiratory infections caused by certain bacteria, such as streptococci, in horses.
• The effectiveness of ampicillin for other bacteria would need to take into account the specific bacteria’s susceptibility and might require different dosing schedules, depending on their minimum inhibitory concentrations (MIC) values.