Etomidate & Metomidate
Application and Cautions
- Imidazole-based non-barbiturate hypnotic agents that act by depression of the central nervous system (Close et al., 1996) and have no analgesic properties (Close et al., 1997).
- Relatively quick acting and highly soluble in water (Brown, 1988; Close et al., 1997; Summerfelt et al., 1990).
- Acceptable for euthanizing fish by immersion (Close et al., 1997).
- Immersion must be followed by a physical or chemical method to cause brain death.
- Immersion method may be weak or ineffectual on fish which breath-hold or breathe air.
- The efficacy of etomidate is pH dependent and it has proven to be more effective in alkaline waters (Amend et al., 1982).
- Temperature influences the toxicity of etomidate, with higher temperatures rendering the drug less toxic (Limsuwan et al., 1983).
Amend D.F., Goven B.A. and Elliot D.G. (1982) Etomidate: effective dosages for a new fish anesthetic. Transactions of the American Fisheries Society 111(3):337-341.
Brown L.A. (1988) Anesthesia in fish. Veterinary Clinics of North America: Small Animal Practice 18(2):317-330.
Close B., Banister K., Baumans V., Bernoth E.M., Bromage N., Bunyan J., Erhardt W., Flecknell P., Gregory N., Hackbarth H., Morton D. and Warwick C. (1996) Recommendations for euthanasia of experimental animals Part 1. Laboratory Animals 30(4):293-316.
Close B., Banister K., Baumans V., Bernoth E.M., Bromage N., Bunyan J., Erhardt W., Flecknell P., Gregory N., Hackbarth H., Morton D.B. and Warwick C. (1997) Recommendations for euthanasia of experimental animals Part 2. Laboratory Animals 31(1):1-32.
Limsuwan C., Limsuwan T., Grizzle J.M. and Plumb J.A. (1983) Stress response and blood characteristics of channel catfish (Ictalurus punctatus) after anesthesia with etomidate. Canadian Journal of Fisheries and Aquatic Sciences 40(11-12):2105-2112.
Summerfelt R.C., Smith L.S., Schreck C.B. and Moyle P.B. (1990) Anaesthesia, surgery and related techniques. In: Methods for Fish Biology (Schreck C.B. and Moyle P.B., eds). Bethesda MD: American Fisheries Society, pp.213-272.
- Etomidate is not registered for veterinary use with fish in Canada; investigators are individually responsible for the use of agents that have not been approved for such use.
Potential Influence on Scientific Data
- As a result of the lack of respiration, increases in blood concentrations of adrenaline and cortisol have been demonstrated in fish anaesthetized with metomidate (Iwama et al., 1989).
- Metomidate concentrations above 3 mg/L have been shown to block the cortisol response, and result in increases in blood lactate levels and haematocrit in Atlantic salmon (Olsen et al., 1995).
Iwama G.K., McGeer J.C. and Pawluk M.P. (1989) The effects of five fish anaesthetics on acid-base balance, hematocrit, cortisol and adrenaline in rainbow trout. Canadian Journal of Zoology 67(8):2065-2073.
Olsen Y.A., Einarsdottir I.E. and Nilssen K.J. (1995) Metomidate anaesthesia in Atlantic salmon, Salmo salar, prevents plasma cortisol increase during stress. Aquaculture 134(1-2):155-168.
- Barbiturates & Derivatives
- Clove oil (Eugenol)
- Electrical Stunning
- Etomidate & Metomidate
- Inert gases
- Inhalant Anesthetics
- Penetrating Captive Bolt
- TMS (MS222, tricaine)