OKLAHOMA CITY (AP) — Oklahoma has secured 20 new doses of the execution drug pentobarbital, Attorney General Scott Pruitt said Wednesday, one month before the state is scheduled to put an inmate to death.

Pruitt said his office and the Department of Corrections spent a year trying to locate more dosages of the anesthetic, which is the first drug in a three-drug mixture used for lethal injections.

Before Wednesday’s announcement, the state had just one remaining dose of pentobarbital.

“It is essential the state be able to provide justice for victims’ families and fulfill our constitutional duty to carry out sentences recommended by jurors,” Pruitt said in the statement.

Death row inmate Michael Hooper filed a federal lawsuit last week, claiming that his execution could lead to cruel and unusual punishment if something went wrong with the state’s lone dose. Hooper has an Aug. 14 execution date.

The motion by attorney Jim Drummond said that with one remaining dose, Oklahoma had no backup plan if the drug fails to render Hooper unconscious. The motion mentioned cases where anesthesia drugs “failed to take hold,” but it didn’t provide specifics.

In April, an Arizona inmate shook for several seconds upon receiving a lethal dose of pentobarbital. In that case, the drug was used by itself.

Drummond said Wednesday he couldn’t comment on what this means for Hooper’s case until he confirms the details with state officials.

“It’s not that I doubt their word, but for my client’s sake I need to ascertain they (the dosages) are current and not expired,” and that process will take some time, he said.

Oklahoma switched to pentobarbital in 2010, and its supply of the drug dwindled to one 5-milligram dose after the drug’s Danish manufacturer, Lundbeck, Inc., restricted its use last year.

In the execution process, pentobarbital is used to render an inmate unconscious, followed by vecuronium bromide to stop the breathing and potassium chloride to stop the heart. Other states use different drugs, including propofol, the anesthetic blamed for Michael Jackson’s death, to do single-drug executions.

Hooper, 39, was convicted of the 1993 fatal shootings of his former girlfriend, 23-year-old Cynthia Lynn Jarman, and her two children, 5-year-old Tonya and 3-year-old Timmy. He declined an opportunity this month to seek clemency from the state’s Pardon and Parole Board.

State law allows the provider of the pentobarbital to remain confidential, Pruitt said.