Anesthetic (MS222) Solution Preparation

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Anesthetic (MS222) Solution

  • Anesthetic (MS222) Solutionalso known as MS222 or TMS or Tricaine Methanesulfonate.
  • The FDA approved two products are Finquel (Argent Chemical Laboratories, Inc., 8702 152 Ave. NE, Redmond,  WA 98052, NADA 42-427) and Tricaine-S (Western Chemical 1269 Lattimore Road Ferndale, WA 98248, ANADA 200-226 ), and also recommended by IACUC to use it.
  • MS222 is the only anesthetic recommended for application on fish that could be accepted as human food and requires a 21 day withdrawal period prior to release or harvest and is only labeled for food fish in the families Ictaluridae, Salmonidae, Esocidae, and Percidae, use with other species should be restricted to the hatchery or laboratory
  • 100 mg/mL solutions of MS222 can be stored in amber jars at 4 °C or -20 °C for 6 mo and still used to effectively anesthetize zebrafish.
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Use of Anesthetic (MS222) Solution

  • Anesthetic (MS222) solution used as an anesthetic and euthanasia agent in fish, amphibians and other cold-blooded animals. 
  • Anesthetic Solution (Buffered MS222) is commonly used to temporarily immobilize fish and amphibians.

Preparation of Anesthetic (MS222) Solution

To prepare 1L of Anesthetic (MS222) Solution, the following materials are required;

MS222 (3-aminobenzoic acid ethyl ester; Sigma-Aldrich A5040) (mw: 165.19 g/mol)1 g0.0061 M
sodium bicarbonate (mw: 84.01 g/mol)700 mg0.0083 M


  1. Prepare 800 mL of distilled water in a suitable container.
  2. Add 1 g of MS222 (3-aminobenzoic acid ethyl ester; Sigma-Aldrich A5040) to the solution.
  3. Add 700 mg of sodium bicarbonate to the solution.
  4. Add distilled water until volume is 1 L.
  5. The resulting pH should be ~7.0. Store in a foil-covered container at 4°C for up to 1 mo. Warm to room temperature before use.


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