Pharmacokinetics of gentamicin in newborn to 30-day-old foals.
Abstract: Gentamicin sulfate, equivalent to 4 mg of gentamicin base/kg of body weight, was administered IV to 6 Thoroughbred foals on day 1 (12 to 24 hours of age) and at 5, 10, 15, and 30 days after birth. On day 40 after parturition, gentamicin was given to the mares at a dosage similar to that used in foals. Decay of serum gentamicin concentrations was best described by a 2-compartment model. Among foals, the overall elimination rate constant at 30 days of age was significantly (P less than 0.05) greater than at days 1, 10, and 15. There was, however, no difference in the overall elimination rate constant between foals and mares. The volume of distribution (Vd), determined on the basis of total area under the disposition curve, did not change between day 1 and day 30. Mean values of Vd of foals were between 1.5 and 2.5 times higher than the mean Vd of the mares; however, only values from the foals at days 5 and 10 were significantly greater. Both age and interindividual differences were reflected in the total body clearance (ClB) of gentamicin. Total body clearance of gentamicin of foals on day 1 was less than that of foals on days 5, 10, and 30. Additionally, C1B of gentamicin on day 15 was less than that on day 30. There was no significant difference between ClB of foals and mares except for the day-30 group, which had a higher clearance rate than did the adults. Protein binding of gentamicin was less than 30% in all groups, and there were no apparent age-related differences.
Publication Date: 1990-12-01 PubMed ID: 2085226
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- Comparative Study
- Journal Article
Summary
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The study investigates the pharmacokinetics (how the body affects a drug) of gentamicin, a common antibiotic, in newborn to 30-day-old foals and their mothers. It reveals that the speed of gentamicin elimination increases in foals as they age and they eliminate the drug similarly to adult horses by day 30. The drug’s distribution and clearance also varies in relation to a foal’s age and individual factors.
Research Method
- Gentamicin was administered intravenously to six newborn Thoroughbred foals at various points during their first 30 days of life, as well as to their mothers at 40 days postpartum.
- The decay of serum gentamicin concentrations was analyzed using a two-compartment model, which separates the body into a central and a peripheral (’tissue’) compartment to better predict the drug’s movement within the body.
Findings
- The researchers found that the overall rate of gentamicin elimination in foals increased with age, showing significant increases from days 1, 10, and 15 to day 30.
- There was no difference in this rate between the day-30 foals and their mothers, implying that by their 30th day, the foals were metabolizing the drug similarly to mature horses.
- Significant interindividual differences were noted among the foals, suggesting individual characteristics can impact how the drug is metabolized.
Volume of Distribution (Vd)
- The Vd is a concept used to describe how a drug is dispersed throughout the body. This study found no changes in the drug’s Vd from days 1 to 30 in the foals.
- However, the Vd was consistently higher in the foals compared to their mothers – sometimes significantly so – indicating the drug spread more extensively within the foals’ bodies.
Total Body Clearance (ClB)
- ClB reflects how efficiently a drug is cleared from the body. The study found age-related differences, with the foals’ gentamicin clearance rates increasing as they grew older.
- By day 30, the foals’ ClB was similar to that of their mothers, except that the day-30 foals had a higher clearance rate.
Protein Binding
- In all tested groups, less than 30% of the gentamicin was protein-bound, a factor that affects a drug’s distribution and elimination. There were no age-related differences in this area.
This study advances understanding of how gentamicin works in young horses, important knowledge since the drug is often used to treat bacterial infections in this demographic. It underscores that foals’ age and individual factors should be considered when prescribing gentamicin to ensure effective and safe treatment.
Cite This Article
APA
Cummings LE, Guthrie AJ, Harkins JD, Short CR.
(1990).
Pharmacokinetics of gentamicin in newborn to 30-day-old foals.
Am J Vet Res, 51(12), 1988-1992.
Publication
Researcher Affiliations
- Department of Veterinary Physiology, Pharmacology, and Toxicology, School of Veterinary Medicine, Louisiana State University, Baton Rouge 70803.
MeSH Terms
- Age Factors
- Animals
- Animals, Newborn / metabolism
- Female
- Gentamicins / administration & dosage
- Gentamicins / blood
- Gentamicins / pharmacokinetics
- Horses / metabolism
- Injections, Intravenous / veterinary
- Metabolic Clearance Rate
- Pregnancy
- Time Factors
Citations
This article has been cited 1 times.- Baggot JD. Clinical pharmacokinetics in veterinary medicine. Clin Pharmacokinet 1992 Apr;22(4):254-73.
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