A Missouri execution postponed last month amid debate over the state's choice of execution drug is set to take place Wednesday.

Allen Nicklasson was convicted in the 1994 slaying of Excelsior Springs businessman Richard Drummond, who stopped to help when a car used by Nicklasson and 2 others broke down on Interstate 70. Another man in the car, Dennis Skillicorn, was executed in 2009.

The execution is scheduled for 12:01 a.m. at the prison in Bonne Terre.

Nicklasson was supposed to be executed Oct. 23, when Missouri planned to use the anesthetic propofol for the 1st time. The plan drew concerns from the medical community because most of the drug is made in Europe, and the anti-death penalty European Union had threatened to limit export if propofol was used in an execution.

As a result, Democratic Gov. Jay Nixon halted the execution.

Days later, the Missouri Department of Corrections announced a switch to pentobarbital. Pentobarbital is a sedative used as an execution drug by 13 other states.

Nicklasson, Skillicorn and Tim DeGraffenreid were driving to Kansas City in August 1994, when their 1983 Chevrolet Caprice broke down on I-70 in mid-Missouri, soon after they burglarized a home and stole guns and money. Drummond, a technical support supervisor for AT&T, saw their stalled car and offered to drive the men to a pay phone.

Once in Drummond's company car, Skillicorn and Nicklasson held a gun to his head and ordered him to drive to a secluded wooded area. Nicklasson shot Drummond twice in the head. His remains were found 8 days later.

Source: Associated Press, December 8, 2013