Intramuscular dosing strategy for ampicillin sodium in horses, based on its distribution into tissue chambers before and after induction of inflammation.

This research focuses on finding the most effective dosing strategy for administering Ampicillin Sodium to horses through intramuscular injection, considering the drug’s distribution into tissue fluid before and after local inflammation.

Methodology

• The study analyzes the Pharmacokinetics (PK) and localization into tissue chamber fluid (TCF) of Ampicillin Sodium injected into six horses.
• The drug concentration-time curves in plasma and TCF were determined subsequent to a dosage administration of 15 mg/kg; this occurred before and after initiating local inflammation with 0.5% carrageenan.
• The parameters derived from this process were then used to simulate potential dosage-dosing interval combinations.

Findings

• In terms of absorption, the administration of Ampicillin was notably rapid and plasma concentrations reached their peak between 18 and 21 minutes following administration.
• Local inflammation did not significantly affect any of the plasma PK parameters; however, inflammation considerably affected both the penetration of Ampicillin into the TCF and its subsequent elimination from there.
• Specifically, the half-life of Ampicillin elimination from the tissue fluid (t1/2(d) was found to be significantly shorter during inflammation.

Simulation of Dosage-Dosing Interval Scenarios

• In modelling various dosage-dosing intervals, the study proposed that a dosage of 15mg of Ampicillin per kg, administered four times daily, would successfully treat all bacteria susceptible to Ampicillin in tissues with good vascular supply.
• Interestingly, a lower dosage of 10mg per kg, administered twice daily, would theoretically be sufficient for treating all Ampicillin-sensitive bacteria in inflamed, poorly vascularized tissues.
• However, reducing the dosage led to a loss in efficacy, which could not be fully compensated by increasing the frequency of administering the drug.

Significance

• The research importance lies in optimized drug administration strategies in equine health and medicine, specifically for dealing with infections.
• The study provides a better understanding of how inflammation affects the distribution of drugs in the body, which can subsequently inform treatment strategies.