Anaesthetics and analgesics used in adult fish for research: A review

Abstract

The number of fish used in research has increased in the last decades. Anaesthesia is required when fish must be held immobile and it is crucial to promote fish welfare, because these vertebrates can show signs of stress and/or pain during handling, transport, tagging, sampling and invasive procedures. The use of an inadequate anaesthetic protocol can compromise not only the welfare of the fish, but also the reliability of the research results. Thus, the development of suitable anaesthetic regimes for each fish species is important. This article reviews the main anaesthetic and analgesic agents used in adult fish in a research setting.

A Comparison of Buffered Tricaine Methanesulfonate (MS-222) and Isoeugenol Anesthesia for Caudal Fin Clipping in Zebrafish (Danio rerio)

“…6 The dose of MS-222 used in the current study was almost 1.7 times the dose used in that study, which indicates the range of doses that may be appropriate for zebrafish anesthesia. 7 Further refinement to the use of MS-222 is required along with further exploration into alternative drugs, which may be safer for both fish and personnel.…”

“…Isoeugenol is soluble in water and is approved in some countries for anesthesia of fish for human consumption, with no withdrawal period. 7 The mechanism of action of isoeugenol is unknown, but may be similar to that of other local anesthetics such as MS-222. 11 As a compound structurally similar to eugenol, isoeugenol may also inhibit sodium, potassium and calcium channels, inhibit NMDA receptors and potentiate GABA A receptors in the same way as eugenol.…”

“…13 The side effects of isoeugenol have not been extensively reported, although more evidence is available for eugenol (also a constituent of clove oil). 7 Eugenol may have a wider safety margin and be associated with a longer induction time and a slower recovery than does MS-222. 3,9 The ideal anesthetic for fish should be easy to administer, effective at a low dose, able to induce anesthesia in less than 3 min with minimal stress, provide immobilization and effective analgesia throughout the procedure, allow recovery from anesthesia within 5 min, and induce no or minimal changes in physiology and behavior.…”

Determination of Optimal Doses and Minimum Effective Concentrations of Tricaine Methanesulfonate, 2-Phenoxyethanol and Eugenol for Laboratory Managements in Nile Tilapia (Oreochromis niloticus)

“…To ensure animal welfare, anesthetic agents are commonly used to induce sedation and/or anesthesia in fish for many occasions such as during netting, weighing, handling, transportation, vaccination, blood sampling, surgery, and scientific researches [ 1 , 2 ]. Depending on the purpose of activity, various degrees of anesthesia stages are implemented.…”

“But It’s Just a Fish”: Understanding the Challenges of Applying the 3Rs in Laboratory Aquariums in the UK

“…For example, does the benefit of analgesia for a social species like a zebrafish outweigh the benefits of remaining in group housing, since isolation is usually necessary to administer it, and in what circumstances? They also include limited knowledge of the potential confounding variables that analgesic agents can introduce into experimental outcomes, a lack of knowledge of the pharmacological effects of different analgesic agents on different species, as well as problems connected with how to recognise and assess the effectiveness of these agents in these animals [102,103].…”