Aqueous humor and plasma concentrations of ciprofloxacin and moxifloxacin following topical ocular administration in ophthalmologically normal horses.

The research article investigates the effectiveness of two eye-drop solutions, ciprofloxacin and moxifloxacin, in penetrating the eye and being absorbed into the body when administered to horses. The study found that moxifloxacin was more effective than ciprofloxacin at reaching and remaining in the eye, making it potentially more useful for treating deep eye infections.

Methodology

• The researchers used seven healthy adult horses with clinically normal eyes for their experiment. Both ciprofloxacin (0.3%) and moxifloxacin (0.5%) were administered to the eyes of six horses each, with the seventh horse serving as a control group.
• After administering seven doses per eye at four-hour intervals, the researchers collected samples of both the aqueous humor (the clear liquid inside the eye) and blood plasma.
• The collection times for samples were immediately after the final dose, 24.25 hours, 24.5 hours, and 25 hours after the final dose.
• The concentration of each drug in the aqueous humor and plasma was then measured using high-performance liquid chromatography.

Results

• Moxifloxacin had significantly higher concentrations in the aqueous humor than ciprofloxacin, indicating that it penetrates the eye more effectively. The mean concentration of moxifloxacin in the aqueous humor was 0.071 micrograms/mL, compared to a mean concentration of 0.009 micrograms/mL for ciprofloxacin.
• Ciprofloxacin concentrations in plasma were below the lower limit of quantification, while moxifloxacin was detectable in all horses at all sample collection times. This shows that moxifloxacin is more readily absorbed into the body systemically.
• The peak value of moxifloxacin in the plasma was 0.015 micrograms/mL at 24 and 24.25 hours, decreasing to less than 0.004 micrograms/mL at 25 hours.

Conclusions

• The results suggest moxifloxacin may be more effective for treating deep corneal or intraocular bacterial infections in horses as it penetrates the eye more successfully than ciprofloxacin.
• Furthermore, moxifloxacin’s detectable presence in plasma even after ocular administration suggests systemic absorption, which might have additional implications for overall treatment efficacy and strategies.