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Experimental study of tetrodotoxin, a long-acting topical anesthetic

Authors
  • Schwartz, Daniel M.
  • Fields, Howard L.
  • Duncan, Keith G.
  • Duncan, Jacque L.
  • Jones, Matthew R.
Type
Published Article
Journal
American Journal of Ophthalmology
Publisher
Elsevier
Publication Date
Jan 01, 1998
Accepted Date
Jul 24, 1997
Volume
125
Issue
4
Pages
481–487
Identifiers
DOI: 10.1016/S0002-9394(99)80188-3
Source
Elsevier
License
Unknown

Abstract

Purpose To determine the effectiveness and toxicity of tetrodotoxin for use as a long-acting topical anesthetic. Methods Four groups of six rabbits each received a 40-μl aliquot of either tetrodotoxin in one of three concentrations (10 mM, 1 mM, or 0.1 mM) or proparacaine 0.5% into the inferior conjunctival cul-de-sac of one eye, with the fellow eye of each rabbit receiving 40 μl of a 60-mM, pH 4.3 sodium citrate vehicle as a control. Corneal sensation was tested for up to 8 hours after administration of drugs, and response was noted by no blink, partial blink without full eyelid closure, and full blink. Slit-lamp examination at 12 and 24 hours after administration and pachymetry before and 24 hours after administration were performed to detect corneal toxicity. Results Rabbits receiving all three concentrations of tetrodotoxin did not demonstrate any ocular irritation, corneal thickening, or signs of systemic toxicity. At a dose of 10 mM, tetrodotoxin produced an anesthetic effect lasting up to 8 hours. At 1 mM, tetrodotoxin was an effective but shorter-acting anesthetic. At 0.1 mM, tetrodotoxin had no significant anesthetic effect. Proparacaine-treated rabbits initially were anesthetic, but this effect was largely gone by 1 hour and completely gone by 3 hours. Conclusions Tetrodotoxin is a long-acting topical anesthetic in the rabbit cornea. Although additional toxicity studies are required, tetrodotoxin may provide an effective, long-lasting topical anesthetic for use in pain control after corneal procedures such as photorefractive keratectomy.

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