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Updated: Sep 21, 2026

Effect of Artificial Tear Formulations on the Metabolic Activity of Human Corneal Epithelial Cells after Exposure to Desiccation
Published on: May 2, 2020
Topical diclofenac sodium decreases the substance P content of tears
Masakazu Yamada1, Masaro Ogata, Masataka Kawai
1Department of Ophthalmology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160, Japan. yamadam@sc.itc.keio.ac.jp
Objective:
To explore the mechanism by which diclofenac sodium eyedrops exert an adverse effect on the cornea.
Methods:
In 10 healthy Japanese volunteers, 0.1% diclofenac sodium solution was instilled into one eye 3 times daily for 2 weeks. Only vehicle was applied to the other eye. Tear samples were taken before drug treatment, at 2 weeks (on the final day of treatment), and at 4 weeks. Prostaglandin E(2) and substance P concentrations in tears were measured using enzyme immunoassays.
Results:
After treatment for 2 weeks, concentrations of both prostaglandin E(2) and substance P in tears from diclofenac sodium-treated eyes had decreased significantly, and both had returned to baseline levels by 4 weeks. No significant changes were seen in prostaglandin E(2) and substance P levels in vehicle-treated eyes at any time points.
Conclusions:
Diclofenac sodium eyedrops concurrently reduced concentrations of prostaglandin E(2) and substance P in tears. Depletion of substance P (a pain-associated neurotransmitter) by diclofenac sodium may promote development of corneal complications.
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