Background
Anticholinergic syndrome (ACS) is produced by the inhibition of cholinergic neurotransmission at muscarinic receptor sites.
Pathophysiology
Substances with anticholinergic properties competitively antagonize acetylcholine muscarinic receptors; this predominantly occurs at peripheral (eg, heart, salivary glands, sweat glands, GI tract, GU tract) postganglionic parasympathetic muscarinic receptors. Anticholinergic substances minimally compete with acetylcholine at other sites (eg, autonomic ganglia).
Central nervous system (CNS) manifestations result from central cortical and subcortical muscarinic receptor antagonism. The degree of CNS manifestation is related to the drug's ability to cross the blood-brain barrier.
Epidemiology
Frequency
United States
Anticholinergic syndrome may be caused by intentional overdose, inadvertent ingestion, medical noncompliance, and geriatric polypharmacy. Systemic effects also have resulted from topical eye drops. Anticholinergic syndrome commonly follows the ingestion of a wide variety of prescription and over-the-counter medications.
Intentional abuse with hallucinogenic plants (eg, Datura stramonium [jimson weed]) and mushrooms (eg, Amanita muscaria) can cause anticholinergic syndrome due to the presence of anticholinergic tropane alkaloids. Scopolamine has been used in beverages as "knockout drops," and several cases of anticholinergic syndrome have been reported following Chinese herbal tea consumption.
According to the American Association of Poison Control Centers (AAPCC), more than 2.4 million cases of human poison exposure were reported to 61 US poison control centers in 2007.[1]
In 2007, the AAPCC National Poison Data System Annual Report documented 8582 single exposures to anticholinergic drugs. Unintentional ingestions accounted for 8109 presentations, intentional ingestions accounted for 297 presentations, and adverse reactions occurred in 141. Moderate morbidity (requiring specific treatment) was reported in 186 cases, major morbidity (life-threatening) in 13, and no deaths were reported.[1]
In 2007, the AAPCC National Poison Data System Annual Report documented 78,130 symptomatic antihistamine presentations with 33,143 specific to diphenhydramine. A total of 5 deaths were attributed to antihistamine toxicity of which 3 were specifically diphenhydramine related.[1]
Patients with severe central manifestations (eg, hallucinations, psychoses, seizures, coma) have the highest morbidity rates.
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