OKLAHOMA CITY – Oklahoma prison officials will continue using a sedative as part of the state’s three-drug lethal injection protocol despite objections from the drug’s manufacturer, a spokesman for the state Department of Corrections said Thursday.

Denmark-based Lundbeck, Inc., producer of the drug pentobarbital, has said it opposes use of the drug in lethal injections and has sent a letter asking the Oklahoma and Ohio not to use it to put inmates to death.

Oklahoma Department of Corrections spokesman Jerry Massie said prison officials had not seen the letter Thursday but “don’t anticipate any changes.”

Alex Weintz, spokesman for Gov. Mary Fallin, and Diane Clay, spokeswoman for Attorney General Scott Pruitt, said members of their respective staffs also had not seen the letter and would withhold comment.

Oklahoma has used the drug in three executions, including two earlier this month. No other executions are scheduled in the state, which used the pentobarbital as the first drug administered in its three-drug lethal injection protocol. The other two drugs are vecuronium bromide, which stops respiration, and potassium chloride, which stops heart activity.

Officials in Ohio announced Tuesday that they would switch to pentobarbital as the sole drug used to put inmates to death.

Pentobarbital is a barbiturate used to induce comas during surgeries to prevent brain damage when blood flow is interrupted, and to reduce possible brain damage following strokes or head trauma. It is chemically related to the same product used to euthanize pets.

Oklahoma and Ohio decided to switch to pentobarbital due to a national shortage of sodium thiopental, the drug previously administered. Lundbeck does not sell the product directly to end users and has no way of preventing either state from using the drug.

Sodium thiopental’s sole U.S. manufacturer, Hospira Inc., of Lake Forest, Ill., also objected to the use of that drug in lethal executions and also had asked states not to use it.

The company announced last week it was discontinuing the product.