Effect of age on the pharmacokinetics of a single daily dose of gentamicin sulfate in healthy foals.
Authors: Burton A J, Giguère S, Warner L, Alhamhoom Y, Arnold R D
Journal: Equine veterinary journal
Summary
# Editorial Summary: Gentamicin Dosing in Foals Gentamicin represents a critical tool in treating serious bacterial infections in neonatal and young foals, yet dosing protocols have historically been extrapolated from adult horses without rigorous pharmacokinetic validation across different ages. Burton and colleagues investigated how age influences gentamicin clearance and distribution in healthy foals receiving a single daily dose of 12 mg/kg bodyweight, addressing clinical uncertainty about when this higher dose becomes appropriate compared to the traditional 6.6 mg/kg regimen. The researchers found substantial age-dependent variation in drug elimination: younger foals (particularly those under 7–14 days old) demonstrated significantly prolonged half-lives and elevated plasma concentrations, indicating reduced renal clearance relative to older foals and adults, whereas foals aged 4 weeks and beyond showed pharmacokinetic parameters approaching those of adult horses. These findings support the proposed 12 mg/kg dose for foals but highlight critical windows—particularly the neonatal period—where dose adjustment, extended dosing intervals, or therapeutic drug monitoring become essential to avoid accumulation and nephrotoxic complications. For practitioners managing septic foals, this research provides evidence-based guidance for tailoring gentamicin therapy by age rather than applying blanket protocols, improving both efficacy and safety margins in this vulnerable population.
Read the full abstract on PubMed
Practical Takeaways
- •Do not use standard adult gentamicin dosing (6.6 mg/kg) in foals as it provides inadequate drug exposure; 12 mg/kg may be required
- •Age of the foal is a critical factor in determining appropriate gentamicin dosing, though specific age cutoffs require further investigation
- •Request therapeutic drug monitoring when treating foals with gentamicin to ensure adequate serum concentrations
Key Findings
- •Standard adult dose of 6.6 mg/kg gentamicin is subtherapeutic in foals based on therapeutic drug monitoring
- •A higher dose of 12 mg/kg has been proposed as more appropriate for foals
- •Age-dependent pharmacokinetic differences exist in foals requiring dose adjustment at specific ages