When administered as their manufacturers intend, the three drugs Arkansas could use in lethal injections next week — if courts allow the executions to proceed — are key products of the pharmaceutical industry. They produce amnesia for patients heading into medical procedures, relax muscles to the point that they don't interfere with knife-wielding surgeons and regulate heart rhythms in cardiac patients.

A state judge ruled Friday that Arkansas cannot inject inmates with the muscle relaxant currently on hand until he addresses a complaint that prison officials obtained the drug improperly. He set a hearing for Tuesday; the executions were due to start Monday. The companies that produced the drugs have said they don't want their products used in executions.

Here is a look at the midazolam, vecuronium bromide and potassium chloride in Arkansas' execution protocol:

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MIDAZOLAM

Arkansas' supply of midazolam, the key drug in the procedure, expires April 30. Monday would be the first time Arkansas would use midazolam in an execution, and the intent is to have it sedate inmates before vecuronium bromide stops their breathing and potassium chloride stops their heart.

"It doesn't block the experience in the moment," anesthesiologist Dr. Joel Zivot of Emory University testified in Little Rock federal court this week. "The pain is still there, but they won't recall it later."

At normal adult doses of around 4 mg, midazolam can slow or stop breathing to the point that medical literature advises doctors to monitor patients closely. With a 500 mg dose listed in the state's execution protocol, Arkansas expects that the inmates will not be aware they are dying.

"Midazolam is an appropriate selection," doctor of pharmacy Daniel Buffington of Tampa, Florida, told U.S. District Judge Kristine Baker.

Doctors testified this week that the drug can "precipitate," in which a portion of the drug converts to a solid in the bloodstream under certain conditions. Pharmacists who studied botched executions noted the phenomena in a paper published in 2015 and said precipitation is "a likely scenario" with large doses.

The U.S. Supreme Court in 2015 authorized the use of midazolam in executions, rejecting claims the drug couldn't adequately sedate inmates.

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VECURONIUM BROMIDE

Vecuronium bromide is a muscle relaxant, but not in the typical sense. Rather than being prescribed for tightness or muscle pain, vecuronium is used to prevent muscles from moving so they don't interfere with surgeons. After receiving the drug, patients must be on a ventilator or they will suffocate.

"How long can you hold your breath?" Zivot asked in court when asked to describe the drug's effects. "If given alone, people would be totally aware" that they were becoming oxygen-deprived. He likened it to being held underwater.

The typical dose is up to .1 mg/kg intravenously, or 8.5 mg for the typical inmate set to die this month. Under Arkansas' protocol, executioners will administer 100 mg, or more than 11 times the typical dose.

Medical supply company McKesson says Arkansas obtained its vecuronium bromide under false pretenses.

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POTASSIUM CHLORIDE

Potassium is essential for maintaining a proper heart rhythm — with levels too high or too low both able to cause cardiac trouble, Zivot said. The anesthesiologist said potassium chloride causes considerable pain when injected and is typically diluted and given over several hours.

He said the drug is typically given in doses of 20 milliequivalents over several hours. Arkansas plans to use 240 mEq immediately after the inmate is injected with vecuronium bromide.

"It's not only painful, it's caustic," Zivot testified. "It will destroy the vein as it passes along its length."

Madan Kharel, who is from the pharmacy school at the University of Maryland-Eastern Shore and has doctorates in pharmaceutical sciences and biochemistry, told The Associated Press this week the paralysis caused by the vecuronium bromide should be sufficient to kill the inmates before the executioner delivers a drug to stop the heart.

"The potassium chloride is just to make sure he is dead. It's a final assurance," he said.