— In a move that sets Virginia apart from other death penalty states, the commonwealth will begin using a new drug to execute prisoners by lethal injection to make up for the unavailability of another drug.

The Virginia Department of Corrections announced Friday that it would begin using rocuronium bromide due to a nationwide shortage of pancuronium bromide. The latter had been used across the country as step two of a three-drug protocol since shortly after the U.S. Supreme Court reinstated the death penalty in 1976. Both drugs paralyze muscles.

So far, all of the other death-penalty states have responded to the shortage by switching to a one-drug regimen: administering a larger, lethal dose of the sedative that traditionally had been used as the first step in the process.

Virginia’s move came as something as a surprise to death penalty experts.

“Texas, Georgia, Ohio, Missouri — all the other major death penalty states — have been switching to a single drug,” said Richard Dieter, executive director of the Death Penalty Information Center. “And I’m not sure what Virginia’s rationale is for not seizing that opportunity to go with a single drug, which I think is the wave of the future.”

Virginia officials declined to comment beyond a one-sentence statement announcing the change.

Virginia has executed 109 prisoners since the death penalty was reinstated, making it the second-biggest death penalty state behind Texas, which has put 483 to death.

Since the Supreme Court ruling, lethal injection has become the most common method of execution across the country, although death row inmates in Virginia still have the option of choosing the electric chair.

Lethal injection by the three-drug cocktail was thought to be a more humane method of execution. But questions have been raised about whether the process really is painless — specifically because of the second step that Virginia is preserving. Because the second drug causes paralysis, it is not known whether the prisoner feels the effects of the third drug, which stops the heart, Dieter said.

“You don’t see motions, you don’t hear groans,” Dieter said. “The second drug has been identified as more cosmetic. . . . It has been criticized as unnecessary to the process except for appearances’ sake. . . . You run the risk with this Virginia process of still having painful executions and perhaps inhumane in the court’s eyes.”

The one-drug protocol is not without its own drawbacks. It takes about 25 minutes for that process to work, compared with 10 minutes with the three-drug regimen, Dieter said. It also represents more of a change in procedure, he said, which could invite more legal challenges.