Drugs & MedicationsEnd of life IssuesHealthcare PolicyHuman InterestProcedures


Capital punishment is the state-sanctioned deliberate taking of another person’s life as retribution for criminal acts performed by that individual. It has existed in one form or another since at least 339 BC when Socrates was forced to take hemlock to end his own life. The methods used over centuries have taken several forms from beheading by the guillotine, to hanging by the neck until dead, firing squads, electrocution, or cyanide gas. These are all effective means to achieve the desired end, but are tainted by the violent nature of their administration and the suffering experienced by the individual. 

It was in the last century that a more humane alternative to the “electric chair” or the “gas chamber” was conceived. That procedure, called lethal injection, was proposed in 1977 and first used in 1982. It involves the intravenous infusion of a drug, or drugs, that alone, or in combination, are capable of killing the person to whom they are given. An intravenous infusion means these lethal drugs are injected directly into the person’s blood stream and immediately have the effect for which they are intended. Each state has a law, or laws, enacted by the legislature that dictate what method of capital punishment is used. However, six states have abolished the death penalty in any form.

So, what is done during a lethal injection? What drugs are used? What effect do they have?

There are six drugs used for lethal injections, and most often a combination of three drugs is used. These drugs have the following effects:

Sedation — an ultra-short acting barbiturate, such as sodium thiopental or sodium pentothal, or midazolam (Versed) is given to sedate, or “knock out” the patient. Nebraska is the only state to use fentanyl for this ‘purpose.

Paralysis — a curare-like drug, pancuronium bromide or succinylcholine, is given to paralyze the body and specifically the muscles for breathing, bringing about chemically-induced asphyxiation. 

Disruption/Cardiac Arrest — a lethal dose of potassium chloride is given to stop the heart. Potassium chloride (KCl) is used as a salt (NaCl) substitute for people who need to restrict sodium in their diet. Larger concentrations of KCl given directly IV interrupt the electrical conduction system of the heart and result in cardiac arrest. 

Each of these drugs alone, at adequate doses, has the potential to be lethal. When administered together, however, the lethality is more certain. Potassium chloride stops the heart. There have been reports from “North Carolina, California, and Virginia ….. potassium chloride in lethal injection did not reliably induce cardiac arrest.” It is KCl that contributes the most to an execution. If it fails, that’s a concern. Is it dosing, administration, or operator error? Some executions have been stopped because an IV could not be started, or the infusion leaked because of the person’s bad veins. These mal-occurrences are not common but get a lot attention from detractors. The majority of lethal injections occur without incident because of adequate preparation.

Twenty-nine states have laws for capital punishment. Twenty-eight use the 3-drug combination for lethal injection. Sedation is achieved within seconds of giving thiopental (how far back from 10 did you count during your last general anesthetic?). Pancuronium interrupts the effect of acetylcholine in the functioning of nerves and muscles causing paralysis. Anesthesiologists and hospitalists use it to paralyze patients to intubate them and mechanically assist their breathing. Intubation and mechanical ventilation are omitted, though, during a lethal injection. Then, an adequate concentration of potassium chloride is given IV disrupting the heart and causing cardiac arrest. Thus within seconds, the effect of the lethal injection is fully noted, and the patient expires. 

In 2022, there were only 18 executions in the U.S. That’s the eighth consecutive year there were fewer than 30 executions nationwide. The sentiment toward capital punishment has shifted in the direction of abolishment as fewer states have legal executions. Medical professional organizations have advocated against the “medicalization” of lethal injections, as well. The American Medical Association, the American Board of Anesthesiology, and the American Nurses Association all have opposed participation in the procedure by their professionals stating their role is to preserve life rather than end it. 

My intent with this blog was to explain what a lethal injection is, what drug regimen is used and what is involved with conducting an execution. Several lethal injections have been botched much to the chagrin of advocates of the practice, but I’m choosing to focus on the mechanics rather than the socially objectionable qualities of this procedure. It’s sedate, paralyze, and disrupt— barbiturate, a curariform drug, then potassium chloride. Lethal injection achieves the desired end result if it is administered carefully and competently.

References: Romanelli F, Whisman T, Fink JL. Issues surrounding lethal injection as a means of capital punishment. Pharmacotherapy 2008 Dec;28(12):1429-1436.

Zimmers TA, Sheldon J, et al. Lethal Injection for execution: chemical asphyxiation. PLoS Med 2097 Apr;4(4):156.

Malcolm DR, Romanelli F. The emergence of second-Generation lethal injection protocols: A brief history. Pharmacotherapy 2917 Oct;37(19):1249-1257.


HTTPS://www.JAMA network.com/journals/JAMA/article-abstract/1874217.


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