Pharmacokinetics of once-daily amikacin in healthy foals and therapeutic drug monitoring in hospitalized equine neonates.

The research article is about a study that examined the pharmacokinetics, or how the drug amikacin is absorbed, distributed, metabolized, and excreted in the body, of healthy young horses as well as those hospitalized. The study also looked at the minimum concentrations (MICs) required for the drug to inhibit the growth of gram-negative bacteria in blood samples.

Study Objectives and Methodology

• The main goal of this research was to explore the pharmacokinetics of once-daily amikacin use in healthy newborn horses, ascertain amikacin concentrations in hospitalized foals, and find out the smallest inhibitory concentrations (MICs) of amikacin required to prevent gram-negative bacteria from septic foals’ blood cultures.
• Administering an intravenous bolus of amikacin (25 mg/kg) to healthy 2- to 3-day-old foals, the study determined their median half-life, clearance, and volume of distribution.

Results

• The results showed 5.07 hours as the median half-life, 1.82 mL/min/kg for clearance and 0.785 L/kg for volume of distribution of amikacin in healthy foals.
• Significant statistical decreases in the area under the curve (14% decrease), mean residence time (19% decrease), and plasma amikacin concentrations (29% decrease) were seen between 2-3 days and 10-11 days.
• In healthy foals, plasma amikacin concentrations at 0.5 hours were significantly higher than those in hospitalized foals. No change in amikacin concentrations was observed due to sepsis, prematurity, and hypoxemia.

Minimum Inhibitory Concentrations (MICs)

• Study discovered that the MIC where 90% of all gram-negative isolates from equine neonatal blood cultures were inhibited by amikacin was 4 microg/mL. This suggests that an amikacin C0.5h (concentration at 0.5 hours) of 40 microg/mL should be targeted to achieve a high serum concentration to MIC ratio of 10:1.
• It was also noted that the proportion of foals with a C0.5h of 40 microg/mL was significantly higher in hospitalized foals receiving a dose of amikacin at 25 mg/kg.

Conclusion and Recommendations

• The research concluded by recommending an initial dose at 25 mg/kg for once-daily amikacin in equine neonates.
• The study highlights the importance of understanding the pharmacokinetics and pharmacodynamics of antibiotics administered to foals, which is crucial for optimizing antimicrobial therapy.