A leading association for U.S. pharmacists adopted a policy Monday that discourages its members from providing drugs for use in lethal injections — a move that could make carrying out such executions even harder for states with the death penalty.

The declaration approved by American Pharmacists Association delegates at their annual meeting held in San Diego this year says the practice of providing lethal-injection drugs is contrary to the role of pharmacists as health care providers.

The association lacks legal authority to bar its members from selling execution drugs, but its policies set pharmacists' ethical standards.

Pharmacists now join doctors and anesthesiologists in having national associations with ethics codes that restrict credentialed members from participating in executions.

"Now there is unanimity among all health professions in the United States who represent anybody who might be asked to be involved in this process," said association member Bill Fassett, who voted in favor of the policy.

The American Pharmacists Association has more than 62,000 members.

Compounding pharmacies, which make drugs specifically for individual clients, only recently became involved in the execution-drug business.

Prison departments turned to made-to-order execution drugs from compounding pharmacies because pharmaceutical manufacturers refused to sell the drugs used for decades in lethal injections after coming under pressure from death penalty opponents.

But now the compounded version is also becoming difficult to come by, with most pharmacists reluctant to expose themselves to possible harassment by death-penalty opponents.

Texas' prison agency scrambled this month to find a supplier to replenish its inventory before getting drugs from a compounding pharmacy it won't identify.

Texas Department of Criminal Justice spokesman Jason Clark said Monday that he had no comment when told about the ruling.

After a troubling use of a two-drug method last year, Ohio said it will use compounded versions of either pentobarbital or sodium thiopental in the future, though it doesn't have supplies of either and hasn't said how it will obtain them. All executions scheduled this year were pushed to 2016 to give the state more time to find the drugs.

Others states are turning to alternative methods.

Tennessee has approved the use of the electric chair if lethal-injection drugs aren't available, while Utah has reinstated the firing squad as a backup method if it can't obtain the drugs. Oklahoma is considering legislation that would make it the first state to allow the use of nitrogen gas as a potential execution method.

Fassett, a professor emeritus of pharmacy law and ethics at Washington State University, said the united front by health professionals might force people to finally face the death penalty's harsh realities.

Lethal injections have created a sterile setting for executions, he said.

"It's like we're not really executing. We're sort of like taking Spot to the vet. We're just putting him to sleep, and that's not true," he said.

Taren Stinebrickner-Kauffman, executive director of SumOfUs.org, an international corporate watchdog organization that has been campaigning for such a policy, said the American Pharmacists Association's stance does not end lethal injection as a form of execution, "though that may well be the outcome."