TUCSON, Ariz. – During the nearly two hours it took for an Arizona death row inmate to die last week, executioners injected him with 15 times the amount of a sedative and a painkiller they originally intended to use, according to documents released Friday.

Records released to Joseph Rudolph Wood’s attorneys show he was administered midazolam and hydromorphone in 50-milligram increments 15 times between 1:53 p.m. and 3:45 p.m. – for a total of 750 milligrams of each drug. He was pronounced dead at 3:49 p.m. after gasping more than 600 times while he lay on the table.

Arizona’s execution protocol calls for 50 milligrams of each drug, although some states use as much as 500 milligrams of midazolam in their execution procedures.

“Those are pretty staggering amounts of medication. They did not shortchange in the dose,” said Karen Sibert, a longtime anesthesiologist and spokeswoman for the California Society of Anesthesiologists.

Sibert, an associate professor at Cedars-Sinai Medical Center, said patients who are sedated before a surgery typically receive no more than 2 milligrams each of midazolam and hydromorphone.

“It would be rare that I would use more than 2 milligrams even for a lengthy surgery,” Sibert said. “If that is accurate, that is absolutely a lethal dose.”

Wood’s attorney, Dale Baich, said the dosage details show why an independent investigation of Wood’s execution by a nongovernmental authority is necessary.

“The Arizona execution protocol explicitly states that a prisoner will be executed using 50 milligrams of hydromorphone and 50 milligrams of midazolam,” he said in a written statement. “The execution logs released (Friday) by the Arizona Department of Corrections shows that the experimental drug protocol did not work as promised. Instead of the one dose as required under the protocol, ADC injected 15 separate doses of the drug combination, resulting in the most prolonged execution in recent memory.”

Wood’s July 23 execution renewed debate about the death penalty and the efficacy of lethal injection. It was the third execution to go awry in the U.S. this year.

States have refused to reveal details about their lethal injection procedures, such as which pharmacies are supplying the drugs and who is administering them, because of concerns about harassment. Woods had filed several appeals that were denied by the U.S. Supreme Court, arguing that he and the public have a right to those details. Such demands for greater transparency have become a new legal tactic in death-penalty cases.

Arizona officials say Wood, who was convicted of a 1989 double murder, never suffered and was completely sedated, but his attorney called it a “horrifically botched execution” that should have taken 10 minutes.