DENVER - The Colorado Department of Corrections has called upon pharmacies to help the state acquiring a lethal injection drug in preparation for a potential execution -- the state’s first in 15 years.

DOC Director Tom Clements sent a letter Tuesday to 97 compounding pharmacies in Colorado asking if they could acquire sodium thiopental or other equally or more effective drugs, The Denver Post reports.

The letter was prompted after the U.S. Supreme Court rejected appeals by Colorado's longest serving death-row inmate, Nathan Dunlap.

"For the first time since 1997, the CDOC is facing the task of carrying out an execution," department Director Tom Clements wrote in the letter sent to the compounding pharmacies, according to the newspaper. "I am reaching out to compounding pharmacies throughout the state of Colorado in order to comply with state law that the CDOC acquire sodium thiopental or other equally or more effective substance to cause death."

Dunlap, who was convicted of killing four people at a Colorado Chuck E. Cheese restaurant in 1993, could become the first inmate executed in the state since 1995.

State law indicates that the department is required to carry out executions using "a lethal quantity of sodium thiopental or other equally or more effective substance sufficient to cause death," the newspaper reports.

Corrections officials have said they never stockpiled sodium thiopental because the state would've had to spend money to replenish the drugs each time they expire.