A variety of techniques have been proposed and employed for the killing of domestic animals but relatively few have survived as suitable agents for euthanasia-namely, the induction of painless, suffering-free death. Some agents, such as strychnine, curariform agents, or potassium salts cause suffering while others have other disadvantages. 'lbday, dogs and cats are commonly euthanatized with sodium pentobarbital or with T-61 which is a mixture of a central nervous system narcotic, a paralytic agent, and a local anesthetic. The use of T-61 was first reported in the United States in 1963 (Quin 1963). The substance gradually became more popular because it was not a DEA-controlled substance and therefore practitioners did not have to deal with the stringent reporting requirements needed for the barbiturates. However, the presence of a paralytic agent in the T-61 mixture, continuing anecdotal reports of bad reactions when using T-61, and the relatively complicated protocol recommended for its administration have resulted in repeated questions being raised about the appropriateness of T-61 as a euthanasia agent.
Rowan, A.N. (1985). T-61 use in the euthanasia of domestic animals: A survey. In M.W. Fox & L.D. Mickley (Eds.), Advances in animal welfare science 1985/86 (pp. 79-86). Washington, DC: The Humane Society of the United States.