Lawyers for a death row inmate in Oklahoma are protesting a state plan to kill their client using a drug typically used to put down animals amid a nationwide shortage of the anesthetic regularly used in executions.
Oklahoma is considering the use of pentobarbital, a drug used to euthanize animals, in the upcoming execution of John David Duty, a convicted murderer scheduled to be executed on Dec. 12.
Across the country, states that implement the death penalty by lethal injection are scrambling to determine alternative ways to kill convicts. Hospira, the maker of sodium thiopental, better known as Pentothal, has announced a suspension of production of the drug because of an unspecified supply problem with the drug's key ingredient.
"We are probably going to look at a number of different options now that we can't use sodium thiopental," said Jerry Massie, spokesman for the Oklahoma Department of Corrections. "We are not sure yet what we'll end up using, but pentobarbital is a strategy we're looking at."
In court documents requesting approval to use pentobarbital, the state called the drug "an ideal anesthetic agent for humane euthanasia in animals," comparing it to the sodium thiopental used as the first part of a three-drug cocktail administered during an execution.
In federal court documents filed Monday, Duty's lawyers argued that using pentobarbital is potentially painful and would be tantamount to torture.
"Pentobarbital is untested, potentially dangerous, and could well result in a torturous execution for Mr. Duty," his lawyers wrote.
"There are risks associated with ... Pentobarbital, especially since the [state executioners] intend to use the drug as part of a 3-drug cocktail," they wrote. "Most notably, Pentobarbital is a slower acting barbiturate than Sodium Thiopental. ... This increases the risk to Mr. Duty of not being fully anesthetized at the time the Vecuronium Bromide and Potassium Chloride are administered, thereby increasing the risk of suffering excruciating pain."
Sodium thiopental, a fast acting barbiturate and general anesthetic, is not used to kill the inmate but numbs him for the two drugs that are administered in its wake.
Vecuronium bromide paralyzes the inmate and shuts down the body's muscular and respiratory systems. Potassium chloride stops the heart, inducing a fatal cardiac arrest.
Oklahoma City federal judge Stephen Friot will hold a hearing on Nov. 19 to determine if the state can use pentobarbital as an alternative anesthetic.
"It is necessary that the first drug work. It eliminates the pain for the next two drugs," Richard Dieter of the Death Penalty Information Center previously told ABCNews.com. "Everybody agrees that two-thirds of this process would be excruciating but for the sodium pentothal."
"A lot about this issue is absurd," he said. "That you run out of the drug is like being short of rope for a hanging. That is the reality here."
Oklahoma executed a death row inmate in October using a dose of sodium thiopental the state obtained from Arkansas.
Death row opponents in the United Kingdom are petitioning their government to prevent the export of the drug to the United States after it was learned that British-supplied vials were used in an execution in Arizona.
ABC News' Brian Braiker contributed to this report.