Pentobarbital and sodium thiopental are anaesthetics, used around the world by doctors and vets on all kinds of patients in a variety of cases. They are also used to render prisoners unconscious in the ten US states that use lethal injection to execute their condemned.

That is, as long as they can obtain the drug. Since pharmaceutical company Hospira stopped manufacturing sodium thiopental in early 2011, there hasn’t been a domestic producer of either drug within the US. American prisons rely on either one of the drugs as the first of the three used in the standard cocktail given to those due to be executed - the others being pancuronium bromide, which paralyses all of the muscles in the body, and potassium chloride, which stops the heart.

A couple of years later, and prisons have started to use up the stockpiles, bought from before production ceased. The result is the rise of new, untested drugs in execution cocktails. Here’s the Guardian from yesterday:

On Thursday, the state of Ohio is scheduled to inject Dennis McGuire, 53, with two drugs: first, the sedative midazolam; then, the painkiller hydromorphone. When it is over, McGuire, who was convicted of the 1989 rape and murder of Joy Stewart, will be dead – which is Ohio’s goal. But the procedure is untried and untested; the drugs that the state will employ have never been used in a death chamber. And experts have warned in legal proceedings that if the process goes wrong, McGuire will not just peacefully drift away, but will be awake, struggling and failing to pull enough air into his lungs, until the drug overdose that will kill him takes hold. "McGuire will experience the agony and terror of air hunger as he struggles to breathe for five minutes after defendants intravenously inject him with the execution drugs," his lawyers have said in court documents. But on Monday a federal judge in Columbus, Ohio, ruled that McGuire's execution could go ahead. Judge Gregory Frost found that there was insufficient evidence to show a substantial risk of severe pain for the condemned man and said that “Ohio is free to innovate and to evolve its procedures for administering capital punishment.” An Ohio state prosecutor, addressing the court, said: "You're not entitled to a pain-free execution.”

That last point is contentious - much of the motivation for making sure that executions are calm and painless is to avoid accusations that they might constitute a “cruel and unusual punishment”, as prohibited by the Eighth Amendment. Lethal injection is used specifically because it is seen as less painful than historical forms of execution, such as beheading, electrocution, or firing squad.

Yet the pretense of kindness relies on there being no struggle from the condemned prisoner. While there is no sure way of knowing the pain that someone experiences when getting the sodium thiopental/pancurium bromide/potassium chloride cocktail, there are several cases of prisoners appearing to be in severe pain. A typical lethal injection death should be completed within seven minutes. Often that time is exceeded, sometimes by one or two hours, and throughout the execution the prisoner can be twitching, shaking, blinking, or appearing to try to speak.

Last week, in Oklahoma, 38-year-old Michael Lee Wilson, convicted of beating a convenience store manager to death in 1995, was executed in what appeared to be considerable distress. His last words, 20 seconds after the execution began, were: “I feel my whole body burning.” It begins to sound like a cruel or unusual punishment.

The prison may have used a batch of pentobarbital that was past its expiration date. Pentobarbital is manufactured by Danish pharmaceutical company Lundbeck. When the domestic US production of the drug stopped in early 2011, that Danish pentobarbital began to find its way to American prisons for use in executions - a situation that caused an unhappy Lundbeck to force its customers to sign an agreement that they would not sell on the drug to any prison authority that could use it for the death penalty.

Then, in late 2011, the EU - which forbids torture and the death penalty in its constitution - introduced strict export controls to stop the sale of drugs like pentobarbital to the US. What pentobarbital made it through would have had an expiration date of a couple of years. It’s no surprise, then, that as that last batch runs out, we’re starting to see a range of alternative drugs introduced by states that refuse to stop executing prisoners.

On 15 October, for the 1986 rape and murder of 21-year-old Angela Crowley, Florida executed 51-year-old William Happ using the sedative midazolam hydrochloride. Allen Nicklasson, 41, was executed for murder on 11 December in Missouri using pentobarbital, after a temporary stay of execution in October after controversy over the alternative drug that the state wanted to use - the general anaesthetic propofol, which is similar to valium, and which has never been used to execute anyone before. The state refused to comment on who manufactured the pentobarbital used, or where it was bought. Here’s Nature on the case:

Propofol, used up to 50 million times a year in US surgical procedures, has never been used in an execution. If the execution had gone ahead, US hospitals could have lost access to the drug because 90 percent of the US supply is made and exported by a German company subject to European Union (EU) regulations that restrict the export of medicines and devices that could be used for capital punishment or torture. Fearing a ban on propofol sales to the United States, in 2012 the drug’s manufacturer, Fresenius Kabi in Bad Homburg, ordered its US distributors not to provide the drug to prisons. “The European Union is serious,” says David Lubarsky, head of the anaesthesiology department at the University of Miami Miller School of Medicine in Florida. “They’ve already shown that with thiopental. If we go down this road with propofol, a lot of good people who need anaesthesia are going to be harmed.”

Several states, led by Ohio, have since 2009 been moving away from the three-drug cocktail towards simply using pentobarbital on its own - it can cause the body’s lungs to stop working when given in high enough doses. However, the difficulty in procurring even that single drug means that not only are alternative drugs being used without much knowledge of their efficacy, prisons are turning to unregulated "compound pharmacies". These are where two or more other drugs are mixed to approximate the effects of another drug - a process that is unreliable at best, and which has led to outbreaks of diseases like meningitis in areas where the method has been tried with prescription drugs.

(There’s further irony here that the nation most responsible for the international War on Drugs is now forced to seek out an alternative dealer - one which peddles an inferior-quality product, with unknown risks attached - now that its preferred brand is unavailable.)

Sticking up for many of the prisoners condemned to die may be difficult for some, considering the crimes they are convicted of, but the death penalty is enough of a medieval anachronism to know that adding in medical experimentation on top is a cruel, tortuous thing to do. International pressure has had some results in affecting those ten death penalty states in America - we have to hope it hasn't stopped here.

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Now listen to Ian discussing why the US is running out of the drugs it needs for executions on the NS podcast: