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OKLAHOMA CITY – The Oklahoma Department of Corrections can now use five different methods to carry out lethal injections.

The new protocol comes after the state announced last week it could not get two of the three drugs it needs to kill Clayton Lockett, a convicted murderer.

Adopting the new methods allows the ODOC  to use wider array of drugs during a nationwide shortage of execution drugs.

Officials said the shortage is because many drug manufacturers are based in European countries and do not support capital punishment.

The new methods allow for a triple-dose of pentobarbital, a drug that concocted controversy when administered in the lethal injection of Oklahoma inmate Michael Wilson, who said “I can feel my whole body burning.”

Another method allows for the combination of midazolam and hydromorphon.

The combination was used in the first time this year in an Ohio execution that took an “unusually long” twenty minutes.

ODOC can also substitute vecuronium bromide, which stops the inmate’s breathing, with comparable agent.

Vercuronium bromide and pentobarbital, which causes unconsciousness, were two of the drugs the state was unable to get earlier this month.

Both drugs were used under the state’s previous lethal injection method.

MORE: Click HERE to view all five lethal injection methods.

The state provided the new methods to the attorneys of two inmates who are to be executed soon.

They are currently suing the state to learn more about the drugs that will be used to kill them.

Earlier this year, convicted murderers Clayton Lockett and Charles Warner filed a lawsuit against the ODOC.

The lawsuit alleges state law keeping the providers of execution drugs a secret could violate their Constitutional freedom from punishment in a cruel or unusual way.

Executions of both men were pushed back from March to April after the state announced it could not secure the drugs it needed to put them to death.

Lockett and Warners’ attorneys argue all direct manufacturers of execution drugs have stopped participating in lethal injections so the only option for the state to get the drugs is through compounding pharmacies.

Those pharmacies are scarcely regulated by the FDA.

However, because the state is not required to disclose the source of its drugs, the attorneys allege we cannot know whether the drugs are manufactured and stored in a safe way.

Staff for the U.C. Berkeley School of Law’s Death Penalty Clinic agreed in a press release.

“As many as four of the five drug combinations in the new protocol would require the use of compounded drugs made by compounding pharmacies,which operate outside of FDA oversight, making it impossible to know if the drugs have been properly prepared and tested in order to ensure the execution will be carried out in a manner that comports with the Constitution.”

The Oklahoma Attorney General’s Office maintains the secrecy law is necessary in order to procure the execution drugs at all.

“This amendment was spurred by a nation-wide shortage of execution drugs, brought on partially by threats of violence and political pressure exerted on suppliers of the drugs,” the Attorney General’s Office wrote in court documents. 

It cites a Missouri compounding pharmacy as an example after it received an emailed bomb threat when the media identified it as an execution drug manufacturer.

It also states The Apothecary Shoppe, a compounding pharmacy in Tulsa, was sued by a Missouri inmate because it was not authorized to distribute in Missouri, yet the Tulsa pharmacy was believed to be manufacturing its execution drugs.

Lockett was convicted of the 1999 killing of Stephanie Nieman in Kay County and raping her friend. He is scheduled for execution April 22.

Warner received the death penalty after the 1997 rape and murder an 11-month-old girl in Oklahoma County. His execution is slated for April 29.

Oklahoma County District Judge Patricia Parish will hear the merits of the drug lawsuit Wednesday.