Application of in vivo microdialysis for investigation of unbound drug concentrations of intravenously administered sulfadimidine in the paranasal sinus mucosa of horses.

This research article presents a study on the use of in vivo microdialysis to track the concentration of an intravenously administered drug, sulfadimidine, in the paranasal sinus mucosa (PSM) of horses. The results indicate that this method can efficiently monitor drug concentrations, supporting effective treatment for sinusitis in horses caused by susceptible pathogens at a dosing interval of 12 hours.

Objective and Methodology

• The goal of this study was to use in vivo microdialysis, a method for continuously monitoring molecular changes in living organisms, to track concentrations of the drug sulfadimidine in the PSM of horses. Sulfadimidine was administered intravenously as part of the combined drug trimethoprim-sulfadimidine.
• Ten healthy adult horses were selected for the study. Concentric microdialysis probes were implanted into the subepithelial layers of the frontal sinus mucosa of horses. After four hours, the drug was administered every 24 hours for a period of two days.

Data Collection and Analysis

• Dialysate and plasma samples were collected at intervals over the 48-hour period and analyzed for concentrations of sulfadimidine.
• These concentrations, along with the relative loss of sulfadimidine from the perfusate (the fluid containing the drug), were used to calculate the PSM concentration.

Results and Conclusion

• All horses successfully underwent the microdialysis probe implantation and subsequent in vivo microdialysis.
• Peak concentrations of sulfadimidine in the PSM were detected at approximately 5-6 hours after each drug administration.
• For 12 hours, the mean PSM sulfadimidine concentration remained above the minimum inhibitory concentration indicative of sulfonamide susceptibility. This suggests that the drug was effective at combating sinusitis caused by susceptible pathogens when administered at intervals of 12 hours.
• The researchers concluded that in vivo microdialysis is a feasible method for continuous monitoring of PSM sulfadimidine concentrations in unsedated horses. The research supports the use of intravenous administration of trimethoprim and sulfadimidine to effectively treat sinusitis caused by highly susceptible pathogens.