Two men were executed in the United States on Wednesday with a drug not yet approved by federal authorities, after the Supreme Court denied one of the inmate's final appeal.
In Texas, which has put to death more people than any other US state, prison authorities said Michael Yowell was pronounced dead at 7:11 pm (0011 GMT).
His execution was delayed by an hour pending his final appeal to the highest court in the land, said Texas Department of Criminal Justice spokesman Jason Clark.
Yowell was sentenced to death for killing his parents when he was 28 years old after stealing money from them to buy drugs. He had also opened a gas valve so that the house would explode.
In Arizona, 71-year-old Edward Schad died at 10:12 am (1712 GMT), prisons spokesman Doug Nick told AFP.
"Well, after 34 years, I'm free to fly away home," said Schad, strapped to the execution table. "Thank you warden. Those are my last words."
Schad was sentenced to death for the 1978 murder of a 74-year-old whose corpse was found with a cord around its neck eight days after he left for a road trip.
Both Schad and Yowell were executed using a lethal injection with a new barbiturate customized by a compounding pharmacy.
The US Food and Drug Administration has not yet approved the drug.
Several US states are facing a shortfall of pentobarbital, an anesthetic used to euthanize animals, since the Danish producer refused to provide it for executing humans.
Yowell had sought to delay his execution by joining two other death row inmates in suing Texas over a change in the source of pentobarbital, warning it has "a high risk of excruciating pain."
Schad had argued that the barbiturate used for lethal injections in Arizona had not been approved by federal regulators.
His case did not go all the way up to the Supreme Court, and his appeals ended in an appeals court. The high court rejected Yowell's appeal.
Texas and several other states have turned to compounding pharmacies to make customized supplies. They face suits from inmates who warn of potentially contaminated products.
Yowell's lawyers said Texas authorities only revealed information about the drug they were going to use for his execution a week before it was set to take place.
"This shift to compounded drugs is a dramatic change from prior practice, making the need for oversight -- now and in the future -- that much more important," Maurie Levin and Bobbie Stratton said.
"Surely this is not the way we want our government to carry out its most solemn duty."
Compounding pharmacies -- which are regulated by local US state authorities and not federal, national ones -- sparked a scandal in November 2012, when one such company was deemed responsible for a deadly meningitis outbreak because of poor hygiene.
Schad and Yowell's were the 29th and 30th executions so far this year in the United States -- the first in Arizona and the 14th in Texas.