Anesthesia is a state of unconsciousness or lack of thought processing. This includes analgesia, anxiolysis, amnesia, unconsciousness and suppression of somatic motor, cardiovascular and hormonal responses to stimulation.


Anesthetics are drugs that induce a state of anesthesia.


Analgesics are drugs that are capable of reducing or eliminating pain without a loss of consciousness.


Barbiturates, including sodium thiopental and pentobarbital, are central nervous system depressants that produce a wide range of effects from relieving anxiety and treating seizure disorders to total anesthesia. Sodium thiopental, long a mainstay of anesthesia practices, is not used in general anesthesia in the United States because it was replaced by superior drugs to induce anesthesia. Pentobarbital is rarely used in anesthesia practice. Barbiturates are categorized by their duration of action.


Benzodiazepines, including midazolam Valium, Ativan, and Xanax, are central nervous system depressants that reliably provide sedation, muscle relaxation, anxiolysis and anticonvulsant effects. They are prescribed orally to treat anxiety disorders and insomnia, and they are used intravenously to reduce anxiety and cause amnesia before general anesthesia and conscious sedation for minor outpatient procedures.

Ceiling effect

The point at which the administration of a drug reaches the maximum possible effect and the administration of more of drug will not produce an additional effect.


Hydromorphone, commonly known under the trade name Dilaudid, is an opioid narcotic clinically used for the treatment of moderate to severe pain.

Hydromorphone has been used as part of a two-drug lethal injection protocol, in combination with midazolam.


Midazolam, commonly known under the trade name Versed, is the shortest acting drug in the benzodiazepine class. Clinically, midazolam is administered to treat anxiety and lightly sedate a patient prior to the induction of anesthesia in a surgical setting. Midazolam has no analgesic or pain-relieving properties and is not FDA-approved as the sole drug to produce and maintain anesthesia during painful surgical procedures.

Midazolam has been used as the first drug in three-drug execution protocols, and in combination with hydromorphone in a two-drug protocol.

Paradoxical reaction

A paradoxical reaction is when a drug does not work as intended, but rather has the opposite effect on an individual.

Pancuronium bromide; Rocruonium bromide; Vecuronium bromide

These drugs are neuromuscular blocking agents that paralyze all voluntary muscles, including the diaphragm, thereby preventing breathing, but have no effect on consciousness or the ability to feel pain. They are used clinically during surgery to produce paralysis to allow for intubation and to prevent movement. Because these drugs also paralyze the diaphragm, patients are provided mechanical ventilation when neuromuscular blocking agents.

States have used one of these three paralytics as the second drug in a three-drug lethal injection protocol.


Pentobarbital is a short-acting barbiturate clinically used to induce and maintain coma during the treatment of severe head trauma. Pentobarbital is also the most common drug used in the euthanasia of animals.

Pentobarbital has been used as the first drug in a three-drug execution protocols, or as the sole drug in single-drug execution protocols.

Potassium chloride

Potassium chloride, also referred to as KCI, is used clinically to treat or prevent low levels of potassium in the blood and also to stop the heart during bypass surgery. Potassium chloride causes extreme burning and pain upon injection and when a sufficient dose reaches the heart, it induces cardiac arrest.

Potassium is used as the third drug in three-drug lethal injection protocols.

Sodium thiopental

Sodium thiopental, also known as sodium pentothal, is an ultra-short-acting barbiturate that was routinely used for the induction of general anesthesia until it was largely replaced by the use of other drugs.

Sodium thiopental has been used as the first drug in a three-drug execution protocols, or as the sole drug in single-drug execution protocols.