3-Quinuclidinyl Benzilate Poisoning Clinical Presentation

Updated: Feb 22, 2021
  • Author: Christopher P Holstege, MD; Chief Editor: Duane C Caneva, MD, MSc  more...
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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, as follows:

  • 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.

  • Depending on the type of employment (overt or covert) and route of dissemination, cases may be grouped or scattered, have a spectrum of exposure symptoms and variability in severity of symptoms.

Physical examination is the key to diagnosing the causative agent.



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."  Marked variations in absorbed dose would occur following an aersolized release and subsequent potential mass human exposures, with the intensity and duration of physical findings dependent on that absorbed dose and the individual patient's pre-existing health conditions.  

Central nervous system manifestations include the following:

  • 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 manifestations include the following:

  • 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 comes into direct contact with 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 may be 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.



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