Ohio Department of Rehabilitation and Correction / AP Dennis McGuire

Ohio executed condemned prisoner Dennis McGuire Thursday with the first use of the controversial two-drug lethal injection method in the U.S. The condemned killer appeared to gasp several times during his prolonged execution, the Associated Press reports.

He made several long snorting sounds over the course of the 15 minutes it took him to die, according to the AP. His stomach rose and fell several times, and he opened and shut his mouth. It was one of the longest executions in the state since Ohio resumed capital punishment in 1999.

Ohio is just the first of many states that will experiment with different drugs to replace sodium thiopental, which has been widely used in lethal injections nationally for years. But the usual three-drug combination is becoming harder to obtain, so states are looking for an alternative.

Ohio’s Department of Corrections confirmed they used the painkiller hydromorphone and the sedative midazolam to execute McGuire. The time of death was 10:53 a.m, and executions usually start at 10am. It’s unclear when executioners administered the drugs.

Lawyers for McGuire, who was sentenced to death for the 1989 rape and murder of 22-year-old Joy Stewart, argued that the use of the new cocktail of drugs was unconstitutional, because McGuire might be conscious as he suffocates to death.

“In the old three-drug combination, each drug was being used for what it was designed for,” Dr. Jonathan Groner, a professor of clinical surgery at the Ohio State University who studies lethal injections, told TIME this week. “But Ohio is taking drugs that are normally used for things like a colonoscopy, and they’re giving massive overdoses to kill people. They’re using them for their toxic side effects.”

MORE: Ohio’s Lethal-Injection Experiment

[AP]