Dhristi JEE 2022-24

BZ: The Inhibitor of Acetylcholine

The BZ symbol stands for benzyl group with a formula C21H23NO3, molecular mass 337.41g/mol, boiling point at 4120C. BZ is a stable, odourless, white crystalline powder, environmentally stable, and slightly soluble in water. Agent BZ is a code name for 3-quinuclidinyl benzilate (BZ). This chemical has anticholinergic activity, ester of glycolic acid. Drugs that obstruct the pathway of acetylcholine are known as anticholinergic; acetylcholine is a neurotransmitter that conveys messages between cells for various body functions. 

3-quinuclidinyl benzilate (BZ) is described by the US Army as a central nervous system depressant as it acts as an inhibitor of acetylcholine at postsynaptic and postjunctional muscarinic receptor points at smooth muscles, exocrine gland, and autonomic ganglia, and the brain.

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BZ can upset the high collaborative functions of memory, problem-solving, concentration, and grasp; high exposure to BZ can result in complete dysfunction of one's ability to perform any military duty. The first mild symptoms occur within one hour of BZ exposure, and the utmost central effects take place after four hours, lingering twenty-four to forty-eight hours. The apex result occurs at eight to ten hours. BZ reduces the effective concentration of acetylcholine at certain points, causing peripheral nervous system effects; the first symptoms are dizziness, ataxia (loss of motor control), nausea, dry mouth, distorted vision, and bewilderment. Gradually the affected person becomes near unconscious, delusional, and illusional.

BZ is one of the most intoxicating anticholinergic psychomimetic known. A small dose can cause hallucination. After exposure to BZ, symptoms occur in three phases. In the first stage, there is extreme restlessness coupled with involuntary spasms. The second phase is characterised by stupor or semi-consciousness requiring sedation. Complex panoramic hallucinations tend to occur in the third phase between twenty-four and forty-eight hours following the exposure, which can be amusing, frightening, or compassionate.

Chemical State 

BZ chemical is solid at room temperature and normal pressure but can be aerosolized, dissolved in a solvent, or transformed into a gaseous state. The chemical is steady enough to be used in explosive mutation; as BZ chemical is odourless and non-irritant, its presence is detected by the occurring symptoms. Exposure to BZ chemical is primarily through inhalation of aerosolized form, systemic absorption through the epidermis, mucous membrane, or ingestion of the liquefied form. The anticholinergic effects on the peripheral nervous system cause perplexity, confabulation, stupor along with illusion, and regression of automatic motor movements.


BZ chemical has been used multiple times in the last four decades, most notably against the VietCong in Vietnam by the US military; it was used by Yugoslavian platoon against Muslims in Kosovo and Bosnia. Vietnamese soldiers and citizens exposed to BZ suffered from long-term neurological effects. Iraq was suspected of having developed a BZ chemical, but UNO could not verify it for inadequate data, and other substantiate proofs. There is no confirming proof that Iraq or coalition forces used it, but the US and British intelligence believed they possessed a substantial quantity of Agent 15, a compound of chemicals including BZ. When the mass is exposed to Agent 15 or BZ chemical, they may share hallucinations and create mass hysteria. 

Treatment for BZ Exposure

Treatment for BZ exposure is generally supportive. The prime danger of affected people comes from the injuries due to erratic behaviours and cardiac arrhythmic effects deriving from severe exposure. Precautionary measures should be adopted as severely affected, and agitated patients are prone to heat-related sickness if other agents do not provide necessary relief supplementary oxygen required to be used. Contaminated clothes must be removed along with a regular decontamination process to avert further absorption of BZ chemicals via the skin. Patients existing in hot and humid climates may suffer from hyperthermia due to dehydration or insufficient water intake.

Physostigmine is the antidote that can be safely and effectively used to treat BZ exposure. The antidote is most effective when used as an intramuscular injection within four hours of exposure. The effect of Physostigmine lasts for an hour requiring recurrent dosage; the drug increases acetylcholine between neurons in the brain. Physostigmine is used successfully to treat carbon monoxide intoxication. Physostigmine is also known as eserine.  

There are several chemical warfare agents that cause a degree of hallucination and other symptoms; all these agents are declared prohibited under the Chemical Weapon Convention effective from 1997 April. The most used chemical warfare agent is 3-quinuclidinyl benzilate (BZ). Due to its inhibiting properties, it affects both the peripheral autonomic and central nervous systems. 

FAQs on Benzyl Group

1. What are anticholinergic drugs?

Anticholinergic chemicals have been extensively used in chemical warfare. They are categorized as incapacitating agents, implying they are not designed for annihilation or severe injury but to result in sufficient disorientation to perform regular tasks, especially military actions. 

One such chemical warfare agent is 3-quinuclidinyl benzilate, also coded as BZ. 3-quinuclidinyl benzilate is stable under normal temperature and pressure and can be disseminated by thermal producing artillery rounds without being inactive. The chemical stays in soil and water for three to four weeks. A mass hallucination occurs when aerosolized BZ is dispersed. The substance is absorbed by inhalation. BZ shuts down the postsynaptic and postjunctional muscarinic receptors in the central nervous system.

2. What are the types of chemical weapon agents?

Major categories of chemical weapon agents are nerve gas such as tabun, VX, cyclohexyl sarin, sarin, and soman. Mustards and lewisite are examples of blistering or vesicating agents. Chlorine, phosgene, and diphosgene are administered as choking gas. Incapacitating agents like BZ are used for hallucination and regression of motor muscle movements. Pepper gas and chloroacetophenone (CS) are used as riot control agents. Adamsite chemical is used to stimulate nausea. These hazardous chemicals are generally stored and transported in liquid form and decapitated in liquid aerosols or vapours. The agents are absorbed in the body through intact skin, respiratory tract, or eyes, depending on the form of the chemical agent. 

3.What are nerve agents?

Tabun (GA), VX, cyclohexyl sarin (GF), sarin (GB), and soman (GD) all have identical chemical structures to the common organophosphate pesticide Malathion. These chemicals primarily stimulate and then paralyse certain nerve communication, although the body and other severe symptoms like seizures. These agents are volatile liquids under normal temperatures prone to evaporation. The most stable agent is VX, which has the viscosity of motor oil, making it more (hundred to hundred fifty times) lethal than sarin when it contacts the victim's skin. A 10mg dose can cause the death of the exposed person. As nerve agents are heavier than air, they tend to settle towards the ground making it more toxic.