Evaluation of concentration of voriconazole in aqueous humor after topical and oral administration in horses.

The study evaluates how effectively a medication called voriconazole, administered both orally and topically, penetrates the ocular tissues of horses and measures its concentration in the blood and potential toxicity signs. The results indicate the drug penetrated the horses’ cornea effectively and had detectable quantities in the aqueous humor (AH) following topical application, also demonstrating penetration into non-inflamed equine eyes after oral administration, with low voriconazole plasma concentrations detected after topical application.

Study Method

• The research involved 11 healthy adult horses and a variety of application methods and doses.
• In six horses, each eye was treated with a single concentration of a topically administered voriconazole solution every 4 hours for seven doses (0.5%, 1.0%, or 3.0%).
• After the final dose, anterior chamber paracentesis was carried out and plasma samples were collected.
• Voriconazole concentrations in aqueous humor (AH) and plasma were measured through high-performance liquid chromatography.
• Five horses received a singular orally administered dose of voriconazole (4 mg/kg), followed by anterior chamber paracentesis, and voriconazole concentrations in AH were measured.

Results and Findings

• The study showed that mean voriconazole concentrations in AH after topical administration varied by the concentration of the solution applied. For instance, 0.5% solution resulted in 1.43 microg/mL, 1.0% solution in 2.35 microg/mL, and 3.0% solution achieved 2.40 microg/mL. Simply put, higher concentration solutions resulted in higher drug penetration into the ocular tissue.
• Only the 3.0% solution induced signs of ocular toxicosis, indicating potential harm caused by overdosage.
• The presence of voriconazole in the plasma was detected for 1 hour after the final dose’s topical administration, regardless of the solution’s concentration.
• Oral administration of voriconazole resulted in an average concentration of 0.86 microg/mL in AH, demonstrating the drug’s ability to penetrate noninflamed equine eyes following oral administration.
• After topical administration, studies found low plasma concentrations of voriconazole.

Significance of the Study

• As voriconazole concentration in AH and plasma were effectively measured and monitored in the study, using both topical and oral administration, this provides valuable insight for veterinary medicine, especially in the treatment of ocular conditions in horses.
• Given the measurable presence in ocular tissues, voriconazole could be a potential therapeutic solution for cornea-related conditions in horses. Its detectable presence in equine AH also signals it can effectively penetrate and act where necessary.
• The evidence of possible ocular toxicosis in the 3.0% solution group serves as a warning for safe dosage considerations.