BACKGROUND

Avertin® was the trade name for the injectable anesthetic tribromoethanol (TBE).  Avertin® was once manufactured as a pharmaceutical-grade drug, but it is no longer available as such.  The use of non-pharmaceutical grade compounds can present a risk to animal welfare due to concerns over consistency, contamination, or preparation.  There are multiple reports in the literature of physiologic harm to animals including ileus, adhesions, and mortality from the use of TBE.^1-5   The NIH Office of Laboratory Animal Welfare (OLAW) has advised IACUCs to critically evaluate the proposed use of TBE and the consideration of alternative methods that avoid or minimize discomfort, distress and pain⁶.

IACUC Policy

IACUC approval is required to use TBE.  Justification for the use of non-pharmaceutical grade TBE must be approved in the IACUC protocol.  Scientific justification must be provided for the inability to use alternative pharmaceutical-grade anesthetics such as isoflurane or ketamine-combinations.  The Wayne State University IACUC recognizes regulatory efforts to strongly justify non-pharmaceutical-grade substances used in animal care and use protocols and does not recommend the use of TBE in rodent studies.

In light of the body of literature detailing serious post-anesthetic effects, inconsistent and variable anesthesia time, effect variability based on rodent strain, and the availability of pharmaceutical grade alternatives (xylazine, ketamine, isoflurane, etc.), the use of TBE in IACUC protocols is limited to that which is scientifically necessary.

IACUC Standard Operating Procedure

TBE must be prepared, stored, and used in the manner described below:

Stock Solution

1. Stock solutions can be prepared on the bench top and mixed.  If applying heat to mix the solution, the mixture must be prepared in a chemical fume hood.   
2. Stock solution is light sensitive and evaporates rapidly.  Do not leave the bottle open longer than is necessary.  Label, date and refrigerate (4-10⁰C) in tightly sealed, dark bottle.
3. Yellowing of the solution indicates toxic degradation products and the stock must be replaced. 
4. Unused stock solution should be discarded after six (6) months.

Working Solution

1. 1. 1. Check the pH (pH must be >5.0), if <5.0 discard. 
      2. Diluents used in making working solution should either be sterile saline or USP phosphate buffered saline.
      3. Label, date and refrigerate (4-10⁰C) when not in use.  Leave out of refrigerator for approximately one hour prior to administration.  Unused working solution should be discarded after two (2) weeks.
      4. Should only be used for a single, short-term sedation event in any animal and not used for repeated sedations.  Additional or repeated uses may be allowed with scientific justification in the IACUC protocol.

References

1. Pekny T, Andersson D, Wilhelmsson U, Pekna M, Pekny M. 2014. Short general anaesthesia induces prolonged changes in gene expression in the mouse hippocampus. Acta Anaesthesiologica Scandinavica 58: 1127-1133.
2. Kiatchoosakun S, Kirkpatrick D, Hoit Bd. 2001. Effects of tribromoethanol anesthesia on echocardiographic assessment of left ventricular function in mice. Comp Med. 51:26-29.
3. Meyer RE, Fish RE. 2005. A review of triboromoethanol anesethesia for production of genetically engineered mice and rats. Lab Anim 34:47-52.
4. Gardner, D.J., J.A. Davis, P.J. Weina, et al. 1995. Comparison of tribromoethanol, ketamine/acetylpromazine, Telazol/xylazine, pentobarbital, and methoxyflurane anesthesia in HSD:ICR mice. Lab Anim Sci 45:199-204.
5. Zeller W, Meier G, Bürki, Panoussis B. 1998. Adverse effects of tribromoethanol as used in the production of transgenic mice. Lab Anim 32: 407-413.
6. NIH Office of Laboratory Animal Welfare. (Jerry Collins, PhD). (2012). "Use of Non-pharmaceutical-Grade Chemicals and Other Substances in Research with Animals Webinar". Retrieved from http://grants.nih.gov/grants/olaw/120301_seminar_transcript.pdf

Approved: 9/2022