Journal of Applied Ichthyology J. Appl. Ichthyol. 28 (2012), 553–564 Received: August 14, 2011 Ó 2012 Blackwell Verlag, Berlin Accepted: December 3, 2011 ISSN 0175–8659 doi: 10.1111/j.1439-0426.2012.01950.x Review Tricaine methane-sulfonate (MS-222) application in fish anaesthesia By N. Topic Popovic1, I. Strunjak-Perovic1, R. Coz-Rakovac1, J. Barisic1, M. Jadan1, A. Persin Berakovic2 and R. Sauerborn Klobucar1 1Laboratory of Ichthyopathology – Biological Materials, Division for Materials Chemistry, Rudjer Boskovic Institute, Zagreb, Croatia; 2Department of Anaesthesiology, University Hospital Clinic, Zagreb, Croatia Summary MS-222 is used for diverse routine operations such as the Tricaine methane-sulfonate (MS-222) is one of the most widely selection of fish, sorting, grading, weight ⁄ length measure- used anaesthetics for poikilotherms worldwide. This paper ments, sampling, labelling, transportation, broodstock anaes- outlines its anaesthetic efficacy and dosage in fish and thesia, gamete collection, physiological data collection, blood legislation for its use, fish stress responses to MS-222 anaes- sampling, health monitoring, vaccination, radio transmitter thesia and its effect on fish physiology and blood properties, implanting and invasive surgery such as implantation of serial pharmacokinetics, genotoxicity, immune response, potential sampling devices (e.g. cannulas, catheters) for the collection of interference with fish hepatic cytochrome P450 spectra, and its bile, blood and urine (Spaeth and Schweickert, 1977; Jennings impact on nerve sensitivity. Key questions arising from the and Looney, 1998; Redman et al., 1998; McKim et al., 1999; available data are analysed, such as regulatory constraints on Tapper et al., 2000; Bowser, 2001; Wagner et al., 2003; its use, the need for the standardization of buffering protocols, Lewbart et al., 2005; Cotter and Rodnick, 2006; Kiessling and interdependencies of the factors impacting the specific et al., 2009; Weber et al., 2009; Brown et al., 2011). Intra- applicative efficacy of MS-222. Current research has provided arterial or tissue implantation of microdialysis probes also an abundance of data on MS-222 use in fish, although the requires the use of MS-222. Fish have been anaesthetised prior applications within these studies are often impractical at the to liver perfusion for the preparation of isolated hepatocytes farming level. Specific emphasis is therefore placed on high- (Kolanczyk et al., 2003). MS-222 is widely used with larval lighting application strategies on a practical basis, presenting and ornamental fish to reduce transport stress, facilitate potential future research on topics that require in-depth handling and sorting, immobilise larvae for force-feeding, analysis (preparation and storage of anaesthetic solutions, study the role of muscular contraction in the development of pre-anaesthetic sedation and stress reduction, cortisol response various skeletal pathologies, limit activity in metabolic studies in aquarium fish, toxicity of MS-222 metabolites, and possible and for various surgical procedures (Guo et al., 1995; Massee immunodepressive properties). Additionally, both from a et al., 1995; Rombough, 2007; Kucuk, 2010; Pramod et al., scientific and practical perspective, it is necessary to have a better 2010). Aeration should be provided unless sedation or anaes- understanding of safety margins, induction, immersion and thesia is of short duration. A controlled overdose is often used recovery times for many (marine and freshwater, farmed and for humanely euthanizing fish prior to the lethal sampling of ornamental) fish species in order to achieve optimal utilization. tissues or blood (Holloway et al., 2004; Sinclair, 2004; Wilson et al., 2009). The aim of this paper is to present a critical review of MS- Introduction 222 application in fish, its efficacy and dosage, genotoxicity, Anaesthesia, euthanasia and sedation of fish, both wild and impact on fish physiology and blood properties, immune captive, are common practices and requirements in aquaculture response issues and fish stress responses, and to give an and experimental procedures. Tricaine methane-sulphonate overview of recent literature reports and advances in the field (MS-222), C9H11O2N+CH3SO3H, also known as ethyl of fish pharmacology. Emphasis has been placed on highlight- m-amino benzoate, tricaine mesilate, m-aminobenzoic acid ing practical application strategies and potential future ethyl ester methanesulfonate and metacaine, has been one of the research. Given the importance of sedating fish within the most widely used anaesthetic agents for poikilotherms world- context of fish welfare, there is a growing trend towards wide since its introduction in 1967. It was originally produced exploring the diverse aspects and proper use of MS-222, which as a local analgesic alternative to cocaine and has been used as has been compounded by the constraints of employing such in humans. However, its value as an anaesthetic for veterinary medicinal products in the aquaculture industry. aquatic animals was soon recognized and its further develop- ment was exclusively for this purpose. Supplied as a white crystalline powder as a 100% pure drug, it is intended for Legal aspects dissolution in water; one of its advantages is a solubility to In recent decades, European legislation regarding veterinary 11%, forming a clear colourless acid solution. A very high lipid pharmaceuticals has introduced restrictions for use of medi- solubility makes it suitable for use in both freshwater and cines in treatment of farm animals; as a result, available seawater (Brown, 1993; EMEA, 1999; Treves-Brown, 2000; veterinary medicinal products for fish are now authorised. The Ortuno et al., 2002; Coyle et al., 2004; Daniel, 2009; Maricch- main document regarding the availability of aquaculture iolo and Genovese, 2011). medicines is the Regulation for the establishment of maximum U.S. Copyright Clearance Centre Code Statement: 0175–8659/2012/2804–0553$15.00/0 554 N. Topic Popovic et al. residue limits (MRL) (CEC, 1990). In its Annex II, MS-222 is significantly reduced. In a separate study Zahl et al. (2009) authorised within the list of substances not subject to MRLs dissolved MS-222 in ionised water and added the solution to designated for finfish, for water-borne use only (CEC, 1990; seawater tanks to evaluate anaesthesia on Atlantic cod (Gadus EMEA, 1999). However, in many European countries there is morhua). Due to the buffering capacity of seawater, MS-222 no registered fish anaesthetic, and the list of pharmaceuticals induced only a minor pH reduction from 7.9 to 7.5. It would licensed for fish varies. For example, MS-222 is not licensed in thus appear that unbuffered MS-222 solutions have higher Spain, Greece or France, while it is permitted in the United safety margins in the seawater. Although saltwater and Kingdom (UK), Italy, Spain and Norway (EFSA, 2008; freshwater with higher alkalinities contain a sufficient buffering Daniel, 2009). Some European countries have limitations capacity to maintain an acceptable pH (Piper et al., 2001; regarding the use of MS-222, such as Italy, where it is Carter et al., 2011), buffering protocols should be standar- approved only for vaccination and research purposes (EFSA, dised, both for experimental and practical farm purposes. 2008). Countries exporting fish into the European Union (EU) It is recommended that MS-222 be buffered with imidazole, are required to demonstrate that they comply with the sodium hydrogen phosphate or sodium hydroxide (Brown, respective EU regulations on the use and withdrawal of 1993; Davis et al., 2008). The most commonly used buffer is anaesthetics. Therefore, potential MS-222 users within Europe sodium bicarbonate (NaHCO3), as a 1 : 2 ratio solution in should consult their regional legislation prior to administra- tank water (Kolanczyk et al., 2003; Pirhonen and Schreck, tion to fish. In the United States MS-222 is approved by the 2003; Wagner et al., 2003). Although there are literature U.S. Food and Drug Administration for use as a fish reports on the use of NaHCO3 in distilled water (Barreto et al., anaesthetic, but only on Ictaluridae, Salmonidae, Esocidae 2007), the water used to anaesthetise fish should be taken from and Percidae (FDA, 2006). The recommended withdrawal time the environment (aquarium, sea cage, tank); distilled or of MS-222 varies among countries. For instance, the U.S.A. deionized water should not be used, as neither possesses any and Norway have a 21-day withdrawal period before the fish buffering capacity (Smit et al., 1977). Bicarbonate-neutralized can be consumed. Canada requires a 5-day withdrawal period MS-222 at pH >7 results in faster (shorter induction time), for water temperatures above 10°C (Wagner et al., 2002; longer lasting and more consistent anaesthesia with reduced Western Chemical, 2008; Kiessling et al., 2009; AFS, 2011), recovery times (Ohr, 1976; Smit and Hattingh, 1979), while the New Zealand 10 days (Ross and Ross, 2008), while in the UK use of unbuffered MS-222 may cause serious epidermal and fish are deemed fit for human consumption after 70 degree corneal damage in fish (Davis et al., 2008). The American days prior to the last MS-222 application (Pharmaq, 2010). Veterinary Medical Association (AVMA) recommends that Although it is reported to be non-mutagenic (Yoshimura et al., only solutions at or exceeding 500 mg ⁄ L need to be buffered 1981; EMEA, 1999; Alpharma, 2001), care should be taken when euthanizing fish (AVMA, 2007). regarding withdrawal if fish are intended for human consump- Users of MS-222 are interested in methods of preparation tion, since MS-222 is regarded as carcinogenic (Pirhonen and and storage of solutions for easier handling. The reported Schreck, 2003). MS-222 should be handled with caution, since shelflife of the substance after dilution or reconstitution varies it may cause skin and respiratory tract irritation (Sigma, 2007). from 12 h (Pharmaq, 2010), 3–10 days (Western Chemical, It has also been reported to cause reversible retinal toxicity 2008), one month (Alpharma, 2001), and up to 3 months (Ross related to chronic occupational exposure, requiring protective and Ross, 2008) if kept in a dark and cool place.