Facing a shortage of its traditional execution drugs, Oklahoma has revised its procedures to include the same two-drug mixture that left an Ohio inmate making gasp-like sounds as his lethal injection was carried out earlier this year, lawyers for two condemned inmates said Monday, according to TheWire.com.

The attorneys said in a court filing that they were notified after business hours Friday that Oklahoma's prison system had adopted five acceptable ways to put death-row inmates to death, TheWire.com reported. All involve multiple doses of sedatives that by themselves could be lethal.

"If the department is going to use one of these other methods, particularly the one that's never been used before, that's really something the courts need to look at and should have an opportunity to review before the department is allowed to use this controversial combo of drugs," Jen Marino, a staff attorney at the University of California Berkeley School of Law's Death Penalty Clinic, said, according to TheWire.com.

The new protocols give the state a larger "veil of secrecy" that the inmates have been fighting against, said Seth Day, among the lawyers representing two Oklahoma inmates challenging the state's refusal to reveal where it obtains its execution drugs, TheWire.com reported.

In the Monday court filing, their attorneys said it appeared that the Oklahoma Department of Corrections could follow any protocol it liked without having to tell the inmate ahead of time, according to TheWire.com. They also said it would allow drugs from unnamed companies, including compounding pharmacies that face less scrutiny from the U.S. Food and Drug Administration than traditional drug makers.

States have had trouble obtaining supplies of lethal drugs after European manufacturers objected to their use in executions and domestic companies feared being singled out for protests, TheWire.com reported.

Some states have gone to compounding pharmacies or have sought to buy drugs from other death-penalty states, according to TheWire.com.

Under Oklahoma's new protocols, the state is allowed to use, in addition to midazolam with hydromorphone, sodium thiopental as a potential substitute for pentobarbital in a three-drug combination, TheWire.com reported.