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(CNN) — Florida is planning to execute a death row inmate Thursday for the first time in more than 18 months using a lethal injection drug that has never been used in the United States.

Unless a stay is issued, Mark Asay, 53, is scheduled to die by lethal injection after 6 p.m. ET.

Asay was convicted in 1988 of the racially motivated murders of two men in Jacksonville the previous year.

A jury found him guilty of killing Robert Lee Booker — who was black — and Robert McDowell. Before he shot Booker, he called him a racial epithet, according to CNN affiliate WJAX.

Prosecutors say he killed McDowell, who was dressed as a woman, after saying he would pay him for sex, the station reported.

The planned execution marks Florida’s first since a US Supreme Court ruling temporarily halted the practice in early 2016, saying the state’s sentencing process was unconstitutional because it gave judges, rather than juries, too much power in deciding whether to execute an inmate.

Since then, Florida passed a law requiring a unanimous jury recommendation for the death penalty, and Gov. Rick Scott rescheduled Asay’s execution for Thursday.

The state will use etomidate as one of three drugs in the lethal injection, marking the first time the sedative has been used in an execution, according to WJAX. Etomidate will be a substitute for midazolam, a controversial drug that has become harder to get because some drug manufacturers don’t want it used in executions.

One midazolam manufacturer, West-Ward Pharmaceuticals, filed a brief in support of eight inmates in Arkansas in April, saying it tries to ensure its medication isn’t used in executions.

This month, the Florida Supreme Court rejected arguments from Asay’s attorneys that the new drug would cause too much pain, according to WJAX. The state’s highest court turned down a motion to block the execution, saying the inmate had not shown it would lead to more pain.