Pharmacokinetic evaluation and safety of topical 1% morphine sulfate application on the healthy equine eye.

The research paper explores the effects and safety of topically applied 1.0% morphine sulfate on the eyes of healthy horses. It tries to understand if this treatment can damage the corneal epithelial cell or lead to ocular or systemic absorption.

Research Methodology

• The team applied topical morphine sulfate (1.0%) to one eye of the six healthy horses. The application occurred every four hours for a span of 72 hours, after which the horses were euthanized.
• The researchers collected serum samples at different stages during the study. Furthermore, they gathered the horse’s aqueous and vitreous humor (the fluids within the eye) immediately following euthanasia
• They used Enzyme-Linked Immunosorbent Assays (ELISA) for morphine quantification in the aqueous, vitreous humor, and serum samples.
• The study also checked for any adverse ocular (eye-related) or systemic effects throughout the experiment.
• The researchers subsequently submitted the treated and control corneas for histopathology (microscopic examination of tissue to study disease).

Research Outcomes

• All horses developed a mild ocular discharge in the eye that received treatment. However, it is not clear whether this discharge was a direct result of the morphine sulfate.
• One horse also developed a fever during treatment.
• Morphine sulfate was detected in the aqueous humor of the treated eye for all horses, signifying ocular absorption.
• Morphine was found in the vitreous humor of 5 of the 6 horses, indicating that the drug had penetrated deeper into the eye.
• Morphine was present in the serum of 5 out of the 6 horses. This result indicates that the morphine sulfate was absorbed systemically to some degree.
• Lastly, no difference was found between the microscopic appearances of morphine-treated and control corneas. This result suggests that the short-term morphine treatment did not detrimentally affect the corneal epithelial cell integrity.

Conclusion

The team concluded that applying topical 1.0% morphine sulfate, at least in the short term, does not seem to cause significant adverse effects, either systemically or ocularly. Further, it signifies that the topical ophthalmic morphine application results in both ocular and systemic absorption.