The synthetic opioid fentanyl is blamed for tens of thousands of overdose deaths in the U.S.
And the U.S. government has ramped up efforts to stem the flow and seize illegal shipments of the drug from Mexico and China.
(SOUNDBITE) (English) U.S. PRESIDENT DONALD TRUMP, SAYING (OCTOBER 26, 2017):
"The flood of cheap and deadly fentanyl."
But at the same time, the same government was considering putting the drug to use... for lethal injection.
In a court filing first reported by Reuters, the U.S. Department of Justice disclosed it had examined fentanyl as it prepared last year to resume executing death row prisoners.
In the end, it decided against adopting the drug for executions.
Attorney General William Barr announced in July his department instead would use pentobarbital when it resumes federal executions later this year.
The return of the federal death penalty will end a de facto moratorium on the punishment put in place by President Barack Obama.
Five federal inmates are scheduled to be executed in December and January.
Like the opioid morphine, fentanyl is sometimes prescribed by doctors to treat pain.
A surge of illegal fentanyl, which is deadly even in minuscule amounts, has been blamed for a spike in overdose deaths in the U.S.
(SOUNDBITE) (English) FLORIDA GOVERNOR RON DESANTIS, SAYING (MARCH 1, 2019):
"When you have people who are having and bringing enough fentanyl in to kills hundred and thousands of people, that's a menace to our society."
At least two U.S. states, Nebraska and Nevada, have already approved fentanyl for capital punishment.
Last year Nebraska became the first state to use it to carry out an execution.