Pharmacokinetics and endometrial tissue concentrations of ticarcillin given to the horse by intravenous and intrauterine routes.

This research article investigates how the antibiotic ticarcillin behaves in a horse’s body when administered intravenously or directly into the uterus. It finds that the volume of fluid used when inserting the antibiotic into the uterus significantly impacts how long high concentrations of the drug remain in the horse’s endometrial tissue.

Introduction and Methodology

• The study was divided into three phases, investigating the pharmacokinetics of ticarcillin in a horse’s body.
• In the first phase, the researchers injected 30 mg/kg of ticarcillin disodium intravenously into healthy mares and measured resulting plasma and endometrial tissue concentrations.
• In the next two phases, the drug was diluted in two different volumes of sodium chloride and administered directly into the uterus, then sample concentrations were measured at various intervals post-administration.

Results: Intravenous Administration

• For intravenous administration, the peak concentration in the endometrial tissue was 12.9 micrograms per gram, achieved 30 minutes after administration.
• The plasma half-life of ticarcillin in the mares was approximately 0.83 hours, with a small standard deviation signifying uniform response between the animals.

Results: Intrauterine Administration

• In the second and third phases of the study, ticarcillin was infused directly into the uterus using two different dilution volumes (250 ml and 60 ml).
• For the higher volume infusion, peak plasma and endometrial concentrations were 2.76 micrograms/ml and above 150 micrograms/g respectively, one hour after administration. These elevated endometrial concentrations lasted at least two hours post-administration.
• When the lower volume was used, peak concentrations were similar but occurred more quickly (45 minutes for plasma and 30 minutes for endometrial tissue).
• However, one hour after administration, endometrial concentrations of ticarcillin were significantly higher with the 250-ml infusion compared to the 60-ml infusion.

Conclusions

• The study concludes that the volume of fluid used to administer ticarcillin into the uterus substantially influences the duration of high drug concentrations in endometrial tissue.
• This impact suggests that fluid quantity should be carefully considered when dosing horses with intrauterine antibiotics to ensure effective treatment.