JOIN USJohn David Duty, 58, who killed a cellmate in 2001, is said to be the first American prisoner to be executed using the sedative pentobarbital at 18.18 local time at the Oklahoma State Penitentiary, the 'BBC' online reported.
A shortage of sodium thiopental in the US forced the state to make the change, it said, adding that the execution took place after a judge's ruling to allow Oklahoma to use the substitute pentobarbital for sodium thiopental was upheld by a federal appeals court this week.
Sodium thiopental, an anaesthetic, is usually used in the state's lethal injection formula, which also includes drugs that paralyse muscles and stop the heart. Oklahoma received a dose of sodium thiopental from Arkansas for an execution in October but was unable to obtain more of the drug, Oklahoma Department of Corrections spokesman Jerry Massie said.
Lawyers representing Duty and two other death-row inmates argued during a court hearing in November that use of the sedative could be inhumane and that inmates could well be conscious but paralysed when other drugs were administered.
"No one who has been put to death has come back and testified about what it felt like," lawyer Jim Rowan, a board member of the Oklahoma Coalition to Abolish the Death Penalty, was quoted as saying.