Aquatics Anesthesia Study Guide

Overview and Clinical Importance

Tricaine methanesulfonate (MS-222), also known as TMS, Tricaine, or Syncaine, is the most widely used anesthetic agent for fish and other aquatic poikilotherms worldwide. It is the only anesthetic approved by the FDA for use in food fish in the United States. MS-222 is a water-soluble compound that produces reversible general anesthesia through immersion, making it essential for procedures including surgery, diagnostic sampling, transportation, spawning, tagging, and euthanasia.

Understanding fish anesthesia is critical for the NAVLE because aquatic medicine questions frequently test knowledge of proper dosing, solution preparation, monitoring parameters, species-specific considerations, and regulatory requirements for food fish.

Pharmacology of MS-222

Chemical Properties

MS-222 (ethyl 3-aminobenzoate methanesulfonate) is a white crystalline powder with the molecular formula C10H15NO5S and molecular weight of 261.29 g/mol. It is an isomer of benzocaine with an additional methanesulfonate group that confers water solubility. Unlike benzocaine, MS-222 does not require organic solvents for dissolution.