Standard Operating Procedure for MS-222 (Ethyl 3-Aminobenzoate Methanesulfonate, Tricaine Methanesulfonate)


Standard Operating Procedure for MS-222 (Ethyl 3-Aminobenzoate Methanesulfonate, Tricaine Methanesulfonate)

EHS SOP #: 007

Version No.: 1.0

Supercedes: N/A

MS-222 Formula



MS-222 is commonly used in University animal research facilities and individual laboratories for anesthesia or euthanasia of fish, amphibians and other aquatic, cold-blooded animals. This document establishes procedures for the safe handling and use of ethyl 3-aminobenzoate methanesulfonate (CAS# 886-86-2), commonly known as MS-222 or Tricaine methanesulfonate. Pharmaceutical grade MS-222 is also available (e.g., Finquel® and Tricaine-S®).

Health Effects

MS-222 is a white powder that is commonly dissolved in water for use as an anesthetic or for euthanasia. It is known to cause skin irritation, serious eye irritation and may cause respiratory irritation. Long-term occupational exposure to MS-222 has been associated with retinal toxicity in humans.1

Regulatory Limits

The Federal Occupational Safety and Health Administration (OSHA) does not have a Permissible Exposure Limit (PEL) for MS-222.


Based on the risk associated with the use of MS-222 the safety procedures outlined below are required by all research staff when working with MS-222.

Administrative Controls

  • Institutional Animal Care and Use Committee (IACUC) protocols that include MS-222 should reference this SOP to verify that the standard operating procedures are being followed.
  • Anyone who handles MS-222 is required to review this SOP and the attached Safety Data Sheet (SDS) prior to work.
  • An eyewash station should be located inside lab spaces and a safety shower should be accessible nearby where MS-222 solutions are prepared and handled.

Engineering Controls

  • When preparing stock solutions, MS-222 powder must be used in a well-ventilated area or in a chemical fume hood.

Personal Protective Equipment (PPE)

  • Nitrile gloves, a lab coat, and safety glasses when handling powder and stock solutions.
  • Nitrile gloves should also be worn when reaching into tanks containing MS-222 or handling animals that have been immersed in MS-222.
  • When in Division of Comparative Medicine (DCM) facilities, PPE use must be consistent with the facility policy.

Waste Disposal

  • Unused powders or solutions of MS-222 will be disposed of as a hazardous material through EHS.

Accidents or Injuries

Spill Procedures

  • Do not attempt to clean-up if you feel unsure of your ability to do so or if you perceive the risk to be greater than normal laboratory operations.
  • If a small spill occurs absorb with absorbent pads. Double bag contaminated solid waste and submit for EHS hazardous material pickup.
  • If a large spill occurs notify others in the area and evacuate room immediately. Contact EHS (919-962-5507) during working hours and 911 if after hours.

Contact Information

Policy Contact

Environment, Health & Safety
1120 Estes Drive
Campus Box #1650
Chapel Hill, NC 27599-1650
Phone: 919-962-5507

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Article ID: 132074
Thu 4/8/21 9:23 PM
Tue 10/18/22 10:49 AM
Effective Date
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08/28/2014 12:00 AM
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Executive Director
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10/17/2022 12:00 AM
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08/28/2014 12:00 AM
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10/17/2025 12:00 AM
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06/24/2014 12:00 AM
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Environment, Health and Safety