Endometrial and serum gentamicin concentrations in pony mares given repeated intrauterine infusions.

The research study investigated the concentrations of gentamicin (an antibiotic) in the uterine tissue (endometrium) and blood serum of pony mares who were subjected to daily doses of intrauterine infusion for five days. Significant differences were found in endometrial and serum drug concentrations based on the presence of two hormones (progesterone and estradiol) in the infusions.

Overview of the Experiment

• The experiment involved six ovariectomized pony mares (females from which ovaries have been removed) that received daily intrauterine infusions for five consecutive days. Each infusion consisted of 50 ml of a 5% commercial aqueous solution of gentamicin (GT).
• The study encompassed three trial treatments: Trial A applied gentamicin infusion only (serving as the control). Trial B involved a combination of progesterone hormone and gentamicin (P + G), and in Trial C, the mares received a mix of estradiol hormone and gentamicin (E + G).

Endometrial Tissue Concentrations of Gentamicin

• After the treatments, researchers measured the GT concentrations in the endometrial tissue. They found that GT concentrations were significantly higher in Trials B and C compared to the control Trial A, both after 24 and 120 hours post-infusion.
• The GT concentration in the endometrium increased significantly in Trial A from 24 to 120 hours. However, there was no significant difference in GT concentrations among all three trials at the 120-hour mark.

Serum Gentamicin Concentrations

• Following the infusions, tests were run to quantify the GT concentration in the blood serum. The results revealed that, regardless of the treatment, the peak serum GT concentration was recorded at 6 hours after each intrauterine infusion.
• The highest overall serum GT concentration occurred in Trial B (involving progesterone) at 78 hours after administering the treatment.
• Upon evaluating daily variances in serum GT concentrations, Trial A exhibited significant differences between readings at 78 and 102 hours. In contrast, there were no considerable differences in serum GT concentrations across different days for trials B and C.
• Serum GT concentrations in Trials B and C were significantly higher than in the control trial A at given specifics times, but there was no significant difference noted between Trials B and C themselves.

Implications

• The presence of the hormones progesterone and estradiol in the gentamicin infusions significantly affected the concentrations of the drug in both the uterine tissue and blood serum of the pony mares. However, the temporally watchable patterns for variances in GT concentration in the serum and endometrial tissue differed.
• This finding could provide essential insights on the pharmacokinetics of gentamicin and potentially improve the administration and effectiveness of gentamicin treatment for intrauterine infections in equine practice.