(AP) — A constitutional rights group is calling for replacing the use of drug combinations in executions with a single drug that would minimize pain and suffering.

The Constitution Project says states should use the most scientifically reliable method in death-penalty cases. That means using only drugs approved by federal regulators for use in humans. The group also is asking that the public to have an opportunity to comment before states adopt lethal injection procedures.

The group says states relying on lethal injection as a means of execution should use a deadly dose of a single anesthetic or barbiturate approved by the U.S. Food and Drug Administration, rather than complex mixtures of drugs, the dosage and administration of which can easily be miscalculated.