Analgesics currently available for the treatment of ophthalmic pain following any intervention are limited by transient effectiveness and undesirable or adverse side effects. The aim of the present study is investigate the analgesic effect of aspirin nanopreparation on ocular pain model in rats.

Aspirin nano-niosomes (ANio) were prepared by the thin film hydration. Appearance, particle size, encapsulation efficiency, zeta potential, and initial stability of ANio were also studied. Topical antinociceptive activity of ANio assessed using the acute model of chemical (eye wiping) nociception in rats. Nociceptive behavior in rats induced by local application of 5 M NaCl solution on the corneal surface. The number of eye wipes was counted during the first 30 min after application of NaCl solution. ANio (0.1, 1 mg/10µl topical) significantly decreased the number of eye wipes. The rat cornea and retina tissue evaluated by light microscopy after H&E staining.

These results indicate the significant topical antinociceptive effect of ANio in comparison with free niosomes and PBS treated control group. ANio has not been associated with any adverse effects or histopathological alterations on cornea and retina of treated rats.

These data suggest ANio may be a safe and effective treatment for postoperative or post-injury ophthalmic pain.