Absorption of neomycin from the equine uterus: effect of bacterial and chemical endometritis.

This study investigates how much of the antibiotic neomycin is absorbed by the uterus of a horse, with particular emphasis on how this changes due to infection or a chemical reaction. The researchers discovered that more neomycin is absorbed under certain conditions, such as during different phases of the horse’s reproductive cycle, or when there’s a bacterial infection or chemical reaction present.

Objective of the Study

The research aimed to understand how equine uteruses absorb neomycin sulphate—a type of antibiotic—under different internal conditions. In particular, the researchers sought to understand how an infusion of beta-haemolytic streptococci (a type of bacteria that can cause infection) and Lugol’s iodine (a solution often used as a disinfectant) would affect absorption rates. The effects of different phases of the animal’s reproductive cycle were also examined.

Methodology

• The scientists measured plasma concentrations of neomycin after intrauterine infusion of 3.3 mg/kg neomycin sulphate. Mares were split into different groups based on the phase of their reproductive cycle and whether they were exposed to bacteria or the iodine solution.
• Bacterial endometritis was induced in some of the mares using an intra-uterine infusion of beta-haemolytic streptococci. This helped the researchers see how an infection in the uterus might affect absorption rates.
• Chemical endometritis was simulated in some mares by infusing 30 ml of 10 per cent Lugol’s iodine solution into the uterus. This allowed the team to study how this reaction might affect neomycin absorption.
• Cervical flushings were examined in infected luteal mares following neomycin infusion to assess possible increased reflux.

Findings

• Mares infected with beta-haemolytic streptococci absorbed about 12% of the infused neomycin, regardless of the reproductive cycle phase.
• Healthy mares in the oestrus phase (part of the reproductive cycle when the mare is sexually receptive) absorbed 6% of the neomycin, while those in the luteal phase (post ovulation stage) absorbed 56%.
• Peak plasma concentrations in infected mares occurred 2 hours after neomycin infusion, which was earlier than in healthy mares.
• Increased reflux of neomycin was noted in infected luteal mares compared to healthy ones based on cervical flushings.
• After infusion with Lugol’s iodine, 31% of neomycin was absorbed by mares in oestrus and 64% by mares in the luteal phase.
• The peak plasma concentration when Lugol’s iodine was introduced occurred 30 minutes after infusion in both reproductive phases indicating an enhanced absorption.

The research revealed that bacterial infection, chemical reaction, and phases of the reproductive cycle can significantly influence the absorption rate of neomycin in equine uteruses. These findings can help guide effective and targeted use of the antibiotic in equine medical interventions.