Bioavailability of amoxycillin in pigs

Area of Science:

• Veterinary Pharmacology
• Animal Health
• Pharmacokinetics

Background:

• Amoxycillin is a widely used antibiotic in swine.
• Optimizing amoxycillin delivery is crucial for effective treatment of respiratory tract diseases in pigs.
• Understanding drug bioavailability across different formulations and administration routes is essential for veterinary medicine.

Purpose of the Study:

• To evaluate the bioavailability (F) of amoxycillin in pigs following intravenous, intramuscular, and oral administration.
• To compare the pharmacokinetic profiles of different amoxycillin formulations, including conventional and long-acting intramuscular options.
• To determine optimal dosing strategies for amoxycillin in pigs, particularly for respiratory infections.

Main Methods:

• Cross-over study design involving intravenous, intramuscular, and oral administration of amoxycillin to pigs.
• Analysis of plasma amoxycillin concentrations using high-performance liquid chromatography (HPLC).
• Pharmacokinetic variable assessment using non-compartmental methods.

Main Results:

• Intravenous amoxycillin exhibited rapid elimination (mean residence time of 1.4 h).
• Intramuscular conventional formulation showed a bioavailability of 0.83, while the long-acting (LA) formulation had a bioavailability of 1.11 with prolonged plasma concentrations.
• Oral bioavailability was lower in fed pigs (0.28) compared to fasted pigs (0.33).

Conclusions:

• Oral amoxycillin dosing alone may be suboptimal for treating pig respiratory diseases due to low bioavailability and reduced intake during illness.
• A combined intramuscular injection followed by oral dosing every 12 hours is a rational treatment approach.
• The intramuscular long-acting amoxycillin formulation (15 mg/kg) can maintain therapeutic plasma concentrations for approximately 48 hours.