Abstract
Abstract: :
Purpose: Oral sumatriptan, a highly selective 5–HT1B/1D agonist, has been shown to be effective in the treatment of intractable eye pain after photorefractive keratectomy. It is not known whether sumatriptan’s analgesic effect following systemic administration is due to effects on the central nervous system and/or a direct effect on the cornea. A serotonin receptor subtype (5–HT7) that is coupled to adenylyl cyclase was recently characterized within human cornea epithelial cells. To investigate the feasibility of topical sumatriptan therapy for ocular surface pain, we studied the biocompatibility of topical sumatriptan in a rabbit model. Methods: Under general anesthesia, we created corneal epithelial defects in one eye of twelve New Zealand white rabbits. The rabbits were assigned to either topical sumatriptan in two different concentrations (0.1mg/100µL and 1.2mg/100µL) or control vehicle solution. The treated rabbits were additionally given sumatriptan drops (0.1mg/100µL) every eight hours post–operatively. The rabbits were monitored for signs of anterior segment toxicity immediately after dosing and every eight hours thereafter. Epithelial defect size was measured daily. After forty–eight hours, the rabbits were euthanized and their eyes processed for histopathologic analysis. Results: There were no significant differences in abrasion size between the control and treatment groups at all time points (p>0.05). Examinations of the anterior segment were similar among the three groups. No histological differences between the treated and untreated enucleation specimens were noted. Conclusions: A topical formulation of sumatriptan appears to be non–toxic and biocompatible in a rabbit model. More studies are warranted to determine its efficacy as a topical corneal analgesic.
Keywords: drug toxicity/drug effects • ocular irritancy/toxicity testing • receptors: pharmacology/physiology