HOUSTON — The U.S. Supreme Court has refused to review an appeal from spared former Texas death row inmate Thomas Whitaker that questioned whether the state’s use of a compounded version of the powerful sedative pentobarbital for executions would cause unconstitutional pain.

The high court Monday offered no comment on its decision refusing the civil rights lawsuit filed by Whitaker and another condemned prisoner, Perry Williams.

Whitaker last week won a rare clemency from Gov. Greg Abbott. An hour before Whitaker was scheduled for execution Thursday, Abbott agreed with the state parole board that his death sentence should be reduced. Whitaker now is serving life without parole.

Whitaker was convicted of arranging a plot that left his mother and brother fatally shot. His father, wounded in the attack, had urged the commutation.