Ohio ? An Ohio killer was put to death in an efficient 10 minutes Tuesday in the first U.S. execution to use a single drug injection instead of the standard three-chemical combination that has come under legal attack because it can cause excruciating pain.

Kenneth Biros, 51, was pronounced dead shortly after one dose of sodium thiopental began flowing into his veins at the Southern Ohio Correctional Facility. The U.S. Supreme Court had rejected his final appeal two hours earlier.

Experts had predicted that sodium thiopental — used in many parts of the world to put pets down — would take longer to kill than the old method. But the 10 minutes it took Biros to die was about as long as it has taken other inmates in Ohio and elsewhere to succumb to the three-drug combination.

Ohio’s switch to one drug was born of a botched execution attempt on another inmate in September, but critics of the three-drug method have long argued that it amounts to cruel and unusual punishment in violation of the U.S. Constitution because it can subject the condemned to extreme pain while leaving them immobile and unable to cry out.