Pharmacokinetics of metronidazole after rectal administration in horses.

This study was aimed at understanding how metronidazole, a drug, behaves within the body of horses when administered rectally.

Experiment Design

• Six healthy horses made up the test group: five mares and one gelding. Each was given a 15 mg/kg body weight dose of metronidazole to simulate a single dose.
• Prior to administration, the feces were manually evacuated from the horse’s rectum. The metronidazole was then administered as a water-based suspension of crushed tablets via a special tube (28-F catheter) inserted 30 cm into the rectum.

Data Collection

• The researchers collected blood samples from the horses immediately following the drug administration and at various intervals up to 14 hours later. They tested these samples to measure the concentration of metronidazole in the bloodstream over time.

Key Findings

• The peak mean serum (bloodstream) concentration of metronidazole was 4.5 micrograms/ml, reached approximately 0.83 hour (about 50 minutes) after the drug was administered.
• Fourteen hours post-administration, the metronidazole concentration had decreased to an average of 0.38 microgram/ml.
• The mean elimination rate constant, which measures how quickly the drug is removed from the body, was 0.23/h. This indicates that roughly a quarter of the drug was eliminated from the body each hour on average.
• The harmonic mean elimination half-life was calculated to be about 3 hours. This means that 50% of the metronidazole present in the body initially was removed within approximately 3 hours after it was administered.

Concluding Remarks and Further Studies

• The study successfully established the pharmacokinetics of metronidazole in horses upon rectal administration. However, the researchers believe more studies are necessary to determine the ideal therapeutic dosage and regimen when administered via this route.