Gentamicin tissue concentrations in equine small intestine and large colon.

This research conducted on horses studied the concentration of the antibiotic Gentamicin in various tissues after an intravenous injection. The study found that the maximum drug concentration in serum, large colon, and jejunum occurred at different times post-injection, with concentrations decreasing in parallel over a 4-hour period.

Methodology

• The experiment was setup on anesthetized horses which were given Gentamicin sulfate intravenously at a dose of 2.2 mg/kg of body weight.
• Over a 4-hour period post-injection, samples were collected from the horses’ jejunum and large colon tissues (each weighing 1 g), serum, and urine.

Observations

• The concentration of gentamicin peaked in the serum at 0.25 hours post-injection.
• The maximum concentration of gentamicin in the large colon and jejunum happened slightly later, at 0.5 hours and 0.33 hours respectively.
• Post-peak, the concentration of gentamicin in these tissues decreased in parallel with serum concentrations and remained detectable at the end of the 4-hour period.

Excreted Gentamicin

• The amount of gentamicin excreted in the urine during the sample collection period ranged from 7.21 mg to 11.91 mg.
• The mean urinary concentration of gentamicin was found to be 57.01 micrograms/ml.
• The fraction of the dose that was excreted unchanged in the urine was 4.8%, indicating that majority of the drug was metabolized in the body.

Pharmacokinetic Analyses

• Analysis of the serum concentration-time data provided a serum half-life for gentamicin of 2.52 hours.
• The volume of distribution was calculated to be 227 ml/kg, and the body clearance rate was found to be 1.12 ml/min/kg indicating the efficiency of the body in eliminating the drug.
• The half-lives of gentamicin in the jejunum and large colon were found to be slightly lesser than the serum half-life, at 1.32 hours and 1.33 hours respectively.