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Nerve Chemical-Warfare Agents

(Nerve Gas; Nerve Agents)

By

James M. Madsen

, MD, MPH, U.S. Army Medical Research Institute of Chemical Defense (USAMRICD)

Last full review/revision May 2019| Content last modified May 2019
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There are many types of chemical-warfare agents that affect different parts of the body. Nerve agents (sometimes incorrectly called "nerve gas") affect how nerves transmit signals to muscles and other nerves. There are several types of nerve agents:

  • G-series agents

  • V-series agents

  • A-series agents

G-series agents, or G agents, include GA (tabun), GB (sarin), GD (soman), and GF (cyclosarin), which were developed by Nazi Germany before and during World War II. V-series agents include VX. V-series compounds were synthesized after World War II. Nerve agents are similar to organophosphate insecticides but are far more potent.

A-series agents, also known as Novichok compounds, are new and much of the information about them is still classified. An A-series agent was used in a 2018 assassination attempt in the United Kingdom.

At room temperature, G agents are watery liquids that vaporize easily. G agents are dangerous both by skin contact and by inhalation. VX is a liquid with the consistency of motor oil that evaporates relatively slowly. None of these agents has a pronounced odor or irritates the skin.

Nerve agents work by blocking an enzyme that breaks down one of the types of chemicals that nerve cells use to send signals to other nerve cells and to muscles (neurotransmitters). Because the signaling chemical, acetylcholine, is not broken down normally, it accumulates and excessively stimulates nerves, muscles, and glands (including tear glands, salivary glands, and sweat glands) throughout the body. At first the stimulated muscles twitch and contract uncontrollably, but later they become fatigued and weaken.

Exposure to nerve agents can cause long-term neurologic and neurobehavioral problems including anxiety, depression, irritability, and memory problems.

Symptoms

Exposure to a nerve agent causes various symptoms depending on the agent, route of exposure, and dose.

Vapor acts quickly. Exposure of vapor to the face causes constricted pupils, runny nose, and chest tightness within seconds. If vapor is inhaled, the person may collapse within seconds.

Liquid nerve agents act more slowly. Exposure to the skin first causes twitching and sweating at the site of exposure. Bodywide effects occur after a delay that can be as long as 18 hours after exposure to a very small droplet of a G- or V-series nerve agent. Even fatal doses usually take up to 20 to 30 minutes to cause symptoms and signs, which may include sudden collapse and seizures without warning. Skin exposure to a small amount of liquid A-series agent may take as long as a day or two to produce symptoms.

Nerve agents stimulate nerve cells in the brain, so people become agitated and confused, and they may develop seizures or become unconscious. Stimulation of nerve cells outside the brain causes nausea, vomiting, and excessive tearing, nasal secretions, salivation, lung secretions, wheezing, digestive secretions (such as diarrhea and vomiting), and sweating. Stimulation of muscle cells causes cramping followed by weakness and paralysis. Weakness of breathing muscles and disruption of the breathing center within the brain is usually the cause of death.

Diagnosis

  • A doctor's evaluation

Doctors base the diagnosis of nerve agent exposure on the person's symptoms and history of exposure. Special laboratory tests can confirm exposure.

Treatment

  • Injections of atropine and pralidoxime

Two drugs, atropine and pralidoxime, can be given for exposure to a nerve agent. Atropine blocks the effects of excessive amounts of the neurotransmitter acetylcholine, which builds up as the result of exposure. Thus, atropine is termed an anticholinergic drug. Pralidoxime and a new drug, MMB-4, help reactivate the enzyme that breaks down acetylcholine.

Before reaching a hospital, prehospital providers can use an autoinjector containing both these drugs to inject the drugs into a large muscle (such as the thigh). Subsequent doses of the drugs are given intravenously.

The skin is decontaminated as soon as possible using a specially formulated commercial topical skin-decontamination product (called Reactive Skin Decontamination Lotion, or RSDL®), a dilute solution of household bleach, or soap and water. First responders inspect any possibly contaminated wounds, remove all debris, and flush the wound with plain or salt water. Severe symptoms and death may still occur because decontamination may not completely remove nerve agents that have already started to pass through the skin.

Doctors typically treat poisoning with nerve agents by aggressively and carefully monitoring people's heart rates, core temperatures, and enzyme levels throughout treatment.

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.

Drugs Mentioned In This Article

Generic Name Select Brand Names
PROTOPAM CHLORIDE
ATROPEN
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
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