After a nearly nine-month delay prompted by a botched lethal injection last spring, Oklahoma plans to execute a death row inmate Thursday with the same three-drug method Florida intends to use about an hour earlier.

Oklahoma prison officials ordered new medical equipment, more extensive training for staff and renovated the execution chamber inside the Oklahoma State Penitentiary to prevent the kind of problems that arose during the execution of Clayton Lockett in April. Lockett writhed on the gurney, moaned and tried to lift his head after he'd been declared unconscious, prompting prison officials to try to halt his execution before he died.

Attorneys for the state say a failed intravenous line and a lack of training led to the problems with Lockett's injection, not the drugs.

Both Oklahoma and Florida plan to start the executions with the sedative midazolam, which has been challenged in court as ineffective in rendering a person properly unconscious before the second and third drugs are administered, creating a risk of unconstitutional pain and suffering.

Charles Frederick Warner, the 47-year-old Oklahoma inmate scheduled to die Thursday, and three other Oklahoma death row inmates have filed a petition with the U.S. Supreme Court to stop their executions.

Oklahoma Attorney General Scott Pruitt said the state Department of Corrections "has responded with new protocols that I believe, prayerfully, will provide them more latitude in dealing with exigent circumstances as they arise." His office has successfully defended Oklahoma's new protocol in federal court.

Oklahoma also has increased by five times the amount of midazolam it plans to use to mirror the exact recipe that Florida has used in 11 successful executions.

But midazolam also was used in problematic executions last year in Arizona and Ohio, where inmates snorted and gasped during lethal injections that took longer than expected.

"There is a well-established scientific consensus that it cannot maintain a deep, comalike unconsciousness," the Oklahoma inmates' attorneys wrote in a petition with the nation's highest court.

Florida plans to execute Johnny Shane Kormonday, 42, for killing a man during a 1993 home-invasion robbery in Pensacola, while Oklahoma intends to execute Warner an hour later Thursday for killing his roommate's infant daughter in 1997 in Oklahoma City.

Pruitt acknowledged that midazolam is not Oklahoma's first choice to be used in lethal injections. But he said state prison officials have been unable to secure other, more effective drugs because the manufacturers oppose their use in executions.

"Pentobarbital is best," the attorney general said. "It's worked in our state, but the manufacturers of pentobarbital will not sell that drug ... to a state for death penalty purposes."

During a three-day hearing last month before a federal judge in Oklahoma City, the Department of Corrections' former top attorney, Michael Oakley, testified that midazolam was selected after he talked to counterparts in other states and conducted his own online research. Oakley also said he reviewed trial testimony from a medical expert who testified about the drug's effectiveness during a legal challenge to its use in executions in Florida.

A state investigation into Lockett's botched execution in Oklahoma last year determined that a single IV line failed and that the drugs were administered locally instead of directly into his bloodstream.

Since then, Oklahoma has ordered new medical equipment such as backup IV lines and an ultrasound machine for finding veins and renovated the execution chamber with new audio and video equipment to help the execution team spot potential problems.