Pfizer’s move to prohibit their drugs from being used in executions has made it even more difficult for states to administer lethal injections.

Last week, Pfizer became the latest and largest pharmaceutical company to ban the use of its products in lethal injections.

The ban marks another in a series of setbacks to the implementation of the death penalty. According to a Gallup poll last fall, the death penalty is still favored by 6 out of 10 Americans.

Lethal injection is the preferred means of execution on the federal level and in the 31 states where capital punishment is legal. Typically, the condemned person is first given an anesthetic to make them unconscious. Then they’re given drugs that stop breathing and induce cardiac arrest.

Because the person is asleep at the time of death, lethal injection is generally considered the most humane means of execution.

Since lethal injection was introduced in the 1970s, sleep has been induced by an anesthetic called sodium thiopental. But the last U.S. manufacturer of sodium thiopental, Hospira, closed its North Carolina plant in 2009.

Since then, American prisons have experimented with other anesthetics, including several still produced by Hospira. Pfizer acquired Hospira last year, assuming control of those products.

Now, they will only be available to buyers who certify that the drugs won’t be resold to prisons, Pfizer officials say.

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In a statement, the company described its policy as ethically necessary.

“Pfizer makes its products to enhance and save the lives of the patients we serve. Consistent with these values, Pfizer strongly objects to the use of its products as lethal injections for capital punishment,” the statement reads.

Similar ethical considerations are cited by professional medical organizations, such as the American Medical Association and the American Nurses Association. Both groups discourage their members from participating in executions.

However, Dudley Sharp, an outspoken death penalty advocate, says the notion that medical professionals are ethically required to steer clear of execution is false.

“Neither the Hippocratic Oath nor ‘do no harm’ have anything to do with executions,” he wrote in a 2015 blog post.

According to medical historian Dr. Howard Markel, Hippocrates wrote, “As to disease, make a habit of two things — to help, or at least, to do no harm.”

Sharp points out that Hippocrates was speaking about treating disease specifically. The issue is about criminal justice, not medical ethics, he says.

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According to the Death Penalty Information Center, there are currently almost 3,000 prisoners on death row in the United States.

To carry out the death penalty, corrections officials are turning to compounding pharmacies, which are more loosely regulated than large pharmaceutical suppliers.

Some states are falling back on older execution methods. Utah, for example, reauthorized use of the firing squad last April.

Sharp says it’s up to the Supreme Court to say which methods of execution are acceptable and which are unacceptable.

“The best method appears to be nitrogen gas — well known as painless, even causing euphoria, acts very quickly, easily accessible, impossible to restrict, easy to administer, using only an oxygen mask and a tank of nitrogen gas, no gas chamber needed, extremely inexpensive,” he told Healthline in an email.

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Recent, highly publicized “botched” lethal injections — in which the condemned person writhed, moaned, or took longer to die than expected — have contributed to the death penalty’s decreasing popularity, David Weiss, a lawyer for the Center for Death Penalty Litigation in Durham, North Carolina, told Healthline.

“Even for the folks that agree it should be done they would also say it should be done with care and with dignity and respect for human life. But when you pull back the curtain it’s very cavalier,” he said. “They’re writing these protocols and not following the protocols.”

But it’s not just the process of execution that is turning people off, Weiss said. The public is also rethinking the fairness and sureness of the judicial system.

“I think jurors are starting to understand that you can never be 100 percent sure whether a person is guilty no matter what the evidence looks like at trial,” he said. “And for that reason it doesn’t make sense to impose a final, irrevocable punishment.”

Those who oppose the death penalty say it’s imposed disproportionately on minorities and the mentally ill.

Sharp argues against the notion that executions have been “botched.” He thinks that the availability of pentobarbital, another anesthetic, will allow for death by lethal injection to continue.

Weiss, however, sees the practice, however it’s performed, as an aging form of justice.

“I think the big thing we can say is either it’s over or it’s heading in that direction. There are just so many things that point to problems with it,” he said. “It’s not a fixable institution.”