eMedicine Specialties > Emergency Medicine > Warfare - Chemical, Biological, Radiological, Nuclear and Explosives

CBRNE - Incapacitating Agents, 3-Quinuclidinyl Benzilate

Author: Christopher P Holstege, MD, Associate Professor of Emergency Medicine and Pediatrics, University of Virginia; Director, Division of Medical Toxicology, Center of Clinical Toxicology; Medical Director, Blue Ridge Poison Ctr, Associate Medical Toxicology Fellowship Director, VA Dept of Health
Coauthor(s): Jennifer S Boyle, MD, PharmD, Fellow in Toxicology, University of Virginia Health System
Contributor Information and Disclosures

Updated: Mar 16, 2010

Introduction

Background

The chemical warfare agent 3-quinuclidinyl benzilate (QNB, BZ) is an anticholinergic agent that affects both the peripheral and central nervous systems (CNS). It is one of the most potent anticholinergic psychomimetics known, with only small doses necessary to produce incapacitation. It is classified as a hallucinogenic chemical warfare agent. QNB usually is disseminated as an aerosol, and the primary route of absorption is through the respiratory system. Absorption also can occur through the skin or gastrointestinal tract. It is odorless. QNB's pharmacologic activity is similar to other anticholinergic drugs (eg, atropine) but with a much longer duration of action.

Also, see eMedicine's article Chemical Warfare Agents.

Pathophysiology

QNB acts by competitively inhibiting muscarinic receptors. Muscarinic receptors primarily are associated with the parasympathetic nervous system, which innervates numerous organ systems, including the eye, heart, respiratory system, skin, gastrointestinal tract, and bladder. Sweat glands, innervated by the sympathetic nervous system, also are modulated by muscarinic receptors. Effects of QNB by any route of exposure are slow in onset and long in duration. The onset of action is approximately 1 hour, with peak effects occurring 8 hours postexposure. Symptoms gradually subside over 2-4 days. Most of the QNB that enters the body is excreted by the kidneys, making urine the choice for detection.

Frequency

United States

Use of QNB against the United States has never been reported. Currently, the US government is funding numerous programs to prepare the nation for potential chemical terrorist attacks against citizens and the military.

International

Use of QNB has been suggested in a number of international conflicts. In January 1992, soldiers in Mozambique experienced an explosion above their troop formation. Subsequent symptoms resembled those expected from QNB. In July 1995, approximately 15,000 people attempted to walk from the enclave of Srebrenica to the free territory in Bosnia.¹ Many experienced hallucinations during their march that were suspected to be secondary to QNB.

Mortality/Morbidity

The LD50 (lethal dose to 50% of an exposed population) for BZ is estimated to be similar to that of atropine, which is approximately 100 mg. Other factors, such as the exposed patient's preexisting health status and the time from exposure to medical care, are also important.

Clinical

History

• An event involving QNB probably would create confusion, panic, multiple seriously ill or dead victims, and a major emergency medical service, police, and/or military response.
  • Large numbers of casualties would overwhelm any community's emergency response.
  • Chaos appropriately would describe events following such an event.
  • In the early phases of an emergency response, the toxin's identification would be unknown, and the history would be misleading and inaccurate.
• Physical examination is the key to diagnosing the causative agent.

Physical

After exposure to QNB, the physical examination is consistent with an anticholinergic syndrome. Characteristics of the anticholinergic syndrome have long been taught using the old medical adage, "dry as a bone, blind as a bat, red as a beet, hot as a hare, and mad as a hatter."

• Central nervous system
  • Depending on the dose and time postexposure, a number of CNS effects may manifest. Restlessness, apprehension, abnormal speech, confusion, agitation, tremor, picking movements, ataxia, stupor, and coma are described.
  • Hallucinations are prominent, and they may be benign, entertaining, or terrifying to the patient experiencing them. Exposed patients may have conversations with hallucinated figures, and/or they may misidentify persons they typically know well.
  • Simple tasks typically performed well by the exposed person may become difficult. Motor coordination, perception, cognition, and new memory formation are altered as CNS muscarinic receptors are inhibited.
• Peripheral nervous system
  • Eye: Mydriasis resulting in photophobia is expected. Impairment of near vision occurs because of loss of accommodation and reduced depth of field secondary to ciliary muscle paralysis and pupillary enlargement. If QNB is splashed into the eye, conjunctival injection and eye pain also occur.
  • Cardiovascular system: Tachycardia is a prominent feature of QNB exposure. Heart rates may be rapid but rarely exceed 150 beats per minute. Exacerbated heart rate responses to exertion also are expected. Systolic and diastolic blood pressure may show moderate elevation. A decrease in capillary tone may cause skin flushing.
  • Gastrointestinal: Intestinal motility slows, and secretions from the stomach, pancreas, and gallbladder decrease. Nausea and vomiting may occur. Decreased or absent bowel sounds are noted on examination.
  • Respiratory: All glandular cells become inhibited, and dry mucus membranes of the mouth and throat are noted. Speech may decrease to a whisper. Breath of the exposed patient may develop a foul odor.
  • Skin: Inhibition of sweating results in dry skin. Place hands directly into the axilla of the exposed patient and note the absence of moisture. Red flushed skin also may occur.
  • Urinary: Urination is difficult or impossible. Subsequent urinary retention may occur, and an enlarged bladder may be palpable on examination.
  • Temperature: The exposed patient's temperature may become elevated from the inability to sweat and dissipate heat. In warm climates such as the desert, this may result in marked hyperthermia.

Causes

Human QNB exposures rarely are reported. Potential causes of exposure to this agent are a laboratory accident, a terrorist event, or a military conflict.

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