What's In a Lethal Injection "Cocktail?"

Christian Sager

Don Bayley/ThinkStock

Lethal injection began as a way to circumvent the ethical objections to "cruel and unusual" methods of execution. But when inmates react to the drugs used in these procedures with seizures and ruptured veins, some have started to ask what's actually in these lethal injection "cocktails" anyway? The current method was first used in Texas in 1982 and has since become the standard method of execution in most of the United States as an "extremely humane" way to end a human life.

Originally, in the late nineteenth century, some proposed using prussic acid (cyanide) as a poisonous method of execution. Even though it had been previously used in gas execution chambers it was still ruled out due to ethical concerns. A century later in 1977, Oklahoma state senator Bill Dawson spearheaded a bill to provide lethal injections for the death penalty because repairing the state's old electric chair was cost-prohibitive. Dawson approached Dr. Stanley Deutsch (chair of Oklahoma University Medical School's Anesthesiology Department) for a recommendation on how to perform such an injection. Deutsch specified the following for his recipe:

By means of a continuous, intravenous administration of a lethal quantity of sodium thiopental combined with either tubocurarine or succinylcholine chloride or potassium chloride, which is an ultra short-acting barbiturate combination with a chemical paralytic agent.

Deutsch went on to tell Dawson, "Having been anesthetized on several occasions with ultra short-acting barbiturates and having administered these drugs for approximately 20 years, I can assure you that this is a rapid, pleasant way of producing unconsciousness." I have to wonder just how often Dr. Deutsch was administering his own unconsciousness, as the sleep-deprived of today would probably enjoy a dose or two of whatever it was he was pleasantly taking.

Deutsch's process was quickly adopted in Oklahoma and spread to other states with death penalties. Here's the preparation for the procedure. First the inmate is connected to an electrocardiogram (EKG) machine to monitor when their heart has stopped and they can be officially declared dead. Then they're restrained and have two intravenous tubes (IV) inserted, one into each arm. A saline solution continually flows through the tubes during the execution.

These tubes run through a hole in the wall, hiding the actual drug-administering execution team from the inmate and any on-site execution witnesses. Automated machines exist to perform a lethal injection execution, but most states perform it manually for fear of mechanical failure. The team members behind the wall are usually prison employees, and not necessarily medical professionals. The prison's warden will signal them to begin injecting the lethal doses of the "triple-drug cocktail." To assuage any guilty consciences, occasionally the team members inject multiple doses, not knowing which one has actually terminated the prisoner. The other doses end up injected into an empty bag. If all goes according to plan, the inmate is declared dead by a medical professional a few minutes after the last drug is administered.

To be clear, the drugs aren't mixed together as the "cocktail" misnomer would suggest. Instead, three drugs are injected in consecutive order. First comes a barbiturate designed to render the prisoner unconscious. Usually this is in the form of the anesthetic sodium thiopental (Pentothal). It only takes 30 seconds for this drug to reach the brain in its clinical concentration. If you were having surgery, you might get 100 to 150 milligrams of this stuff before the doctors start cutting you open. For executions, up to 50 times that (5 grams) can be injected into a prisoner. By itself, this is considered a lethal dose, strong enough to shut down basic body functions like circulation and breathing.

But not all prisons deliver exactly 5 grams. So a change in delivery levels could potentially be inadequate for the execution, especially depending on the prisoner's size, weight and previous drug usage. Some researchers have looked at the post-mortem toxicology reports of the executed and found the concentration levels of thiopental to be less than what would normally be required for surgery. Without enough anesthesia, the inmate would experience asphyxiation, severe burning, muscle cramping and finally cardiac arrest.

Obtaining sodium thiopental isn't exactly easy for executioners either. There's a shortage of the drug within America and manufacturers in Europe have placed an embargo on the drug if it's to be used in an execution. Some prisons have switched to pentobarbital as a replacement anesthetic. It's also a barbiturate that depresses the central nervous system, but is more often used by veterinarians on animals. Both drugs get into human brain tissue and stimulate GABA receptors that reduce the firing of neurons, essentially putting the brain to sleep. The main difference between sodium thiopental and pentobarbital is how quickly they act. The former has a fast onset and doesn't last as long, where pentobarbital is a long-acting drug, sometimes used by hospitals to induce comas in brain-damaged patients.

After one of these barbiturates has taken effect, the team flushes the intravenous line with more saline solution and then injects drug number two, the paralyzing agent pancuronium bromide (Pavulon). Again, while a normal surgical dose is between 40 to 100 micrograms, executioners use up to 100 milligrams of this muscle relaxant. At these levels it causes the inmate to cease breathing due to the paralysis of their intercostal muscles and diaphragm. While it paralyzes the inmate's entire body, this agent also masks any signs of pain they might be experiencing. As alternates, some prisons have used tubocurarine chloride or succinylcholine chloride for similar effect.

Finally, after another saline solution flush, the third drug of potassium chloride is injected into the inmate to induce a cardiac arrest by interrupting electrical signals essential to heart functionality. Considered toxic at only 20 milligrams, a lethal injection of potassium chloride is given in a dose of 50 to 100 milligrams. Some argue that potassium chloride doesn't speed up the time of death in executions, suggesting that the inmates are instead dying from the second drug's induced asphyxiation. Other anesthesiologists reject this idea based on the investigated postmortem drug levels of the executed.

Interestingly, the American Veterinary Medical Association's panel on euthanasia prohibits the use of both pentobarbital and neuromuscular blocking agents to kill animals. They say the combination risks unrecognized consciousness within an animal and without proper training, administrators may not be aware that they're causing the animal pain. This is often used as one of the main arguments against human lethal injection by its critics. Since the American Medical Association prohibits its members from being involved in executions, often the executioners don't have the experience to recognize when the thiopental hasn't fully knocked the inmate unconscious. And when inmates have damaged veins from intravenous drug use, it's even more difficult for these untrained executioners to find a place to insert a needle, much less tell whether the anesthetic was enough to compensate for a drug users' built up immunity.

Now that we know the ingredients in a lethal injection, do they successfully evade the "cruel and unusual" punishment argument of their detractors? Or do we need to investigate even smoother ways to kill our prisoners?