DALLAS — Texas, the nation’s most active death penalty state, announced Tuesday that it would become the latest to switch to single-drug executions amid a drug shortage that has left states scrambling for acceptable alternatives.

The Texas Department of Criminal Justice said it will begin using a single dose of the sedative pentobarbital to carry out death sentences. It had been using that drug in combination with two others, but its supply of one of the other drugs expired.

Texas began using pentobarbital last year after another drug, sodium thiopental, became unavailable when its European supplier bowed to pressure from death penalty opponents and stopped making it.

And now pentobarbital is in short supply after its Danish manufacturer said it would try to prevent its use in executions.

An Oklahoma inmate asked a federal court Tuesday to halt his upcoming execution because that state has only one dose of pentobarbital left. A lawyer for Michael Hooper said Oklahoma has no backup plan if the drug does not render Hooper unconscious, and that creates a risk of cruel and unusual punishment.

Texas officials said in May that they have enough doses of pentobarbital to carry out 23 executions. No one has been executed in the state since.

In the three-drug cocktail, Texas officials administered 5 grams of the drug to render the inmate unconscious, followed by the muscle relaxant pancuronium bromide, then potassium chloride to stop the heart. Pancuronium bromide is the drug that expired.

Department of Criminal Justice spokesman Jason Clark said officials didn’t expect the dose of pentobarbital needed to change with the new procedure.

Four other states — Arizona, Idaho, Ohio and Washington — have used a single drug to carry out executions, according to the Death Penalty Information Center.