In most states the drug is the lethal part of a battery of drugs, administered as a final death blow following drugs intended to relax muscles and render the convict unconscious.
In Ohio, however, the inmate receives just one drug.
Ohio was able to change the protocol without legislation, said Ohio Department of Corrections spokesman Carlo Loparo. But in other states such a change could require lengthy procedures, further drawing out executions and raising greater questions about their legality.
Texas, which has the busiest death row in the country, expects to run out of its supply of lethal drugs in March.
"The supply expires in March, so we'll have to look to some sort of alternative," said Texas Department of Corrections spokesman Jason Clarke. "We'll likely end up changing the drug. We'll look to what other states use successfully."