Arizona used a two-drug protocol for Wednesday's execution of Joseph Rudolph Wood, who had been sentenced to die for the 1989 deaths of a former girlfriend and her father.

Witnesses saw Wood gasp and snort for an hour and 40 minutes after the execution drugs were injected in his veins. He finally was pronounced dead an hour and 57 minutes after the process started.

Executions without problems typically take 10 minutes or so.

While no one knows why Wood's execution lasted so long, a common denominator for three lengthy executions this year is midazolam, a sedative often given to patients prior to surgery. It's commonly known as Versed.

Midazolam's side effects can include serious breathing problems and cardiac arrest. Warning labels that accompany the drug say monitoring is required in case there is a need to intervene with life-saving medical treatment. Overdoses can result in a slow heart rate. A normal dose is usually less than 5 milligrams.

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IN ARIZONA:

Arizona's protocol calls for 50 milligrams of midazolam. The second drug in Wood's execution was the painkiller hydromorphone. At nonlethal doses, it changes the way the brain and nervous system respond to pain. At high doses, the narcotic can stop the respiratory system and the heart.

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IN OHIO:

Midazolam and hydromorphone are the same drugs Ohio used in the January execution of Dennis McGuire, who snorted and made gasp-like sounds during the 26 minutes it took him to die. Ohio used 10 milligrams of midazolam, but then announced it was increasing the dosage to 50 milligrams in the wake of McGuire's execution.

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IN OKLAHOMA:

Oklahoma inmate Clayton Lockett died 43 minutes after his execution began in April — of an apparent heart attack after the state's prison's chief directed the executioner to stop administering lethal doses of three drugs: midazolam, vecuronium bromide and potassium chloride. In executions, they are typically injected in that order, at high doses. Oklahoma's protocol calls for 100 milligrams of midazolam.

Vecuronium bromide is a muscle relaxant used during some surgeries and also can cause breathing difficulties. Potassium chloride is used to treat potassium deficiency but is used in executions to stop the heart.

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IN FLORIDA:

Florida executioners have also used midazolam as part of that state's procedures. Florida's protocol calls for 500 milligrams of the drug.

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Source: National Institutes of Health.