When a significant amount of an anticholinergic is taken into the body, a toxic reaction known as acute anticholinergic syndrome may result. This may happen accidentally or intentionally as a consequence of recreational drug use. Anticholinergic drugs are usually considered the least enjoyable by many recreational drug users, possibly due to the lack of euphoria caused by them. There have been reported cases of users experiencing what they attribute to "euphoria" from the use of this substance. In terms of recreational use, these drugs are commonly referred to as deliriants. The risk of addiction is low in the anticholinergic class. The effects are usually more pronounced in the elderly, due to natural reduction of acetylcholine production associated with its use.
Long term use increases the risk of both mental and physical decline. It is unclear if they affect the risk of death generally. However, in older adults they do appear to increase the risk of death. Possible effects of anticholinergics include:
Acute anticholinergic syndrome is reversible and subsides once all of the causative agent has been excreted. Reversible anticholinesterase Acetylcholinesterase inhibitor agents such as physostigmine can be used in life-threatening cases. Wider use is discouraged due to the significant side effects related to cholinergic excess including: seizures, muscle weakness, bradycardia, bronchoconstriction, lacrimation, salivation, bronchorrhea, vomiting, and diarrhea. Even in documented cases of anticholinergic toxicity, seizures have been reported after the rapid administration of physostigmine. Asystole has occurred after physostigmine administration for tricyclic antidepressant overdose, so a conduction delay (QRS > 0.10 second) or suggestion of tricyclic antidepressant ingestion is generally considered a contraindication to physostigmine administration.
Several narcotic and opiate-containing drug preparations, such as those containing hydrocodone and codeine are combined with an anticholinergic agent to deter intentional misuse. Examples include Hydromet/Hycodan (hydrocodone/homatropine), Lomotil (diphenoxylate/atropine) and Tussionex (hydrocodone polistirex/chlorpheniramine). However, it is noted that opioid/antihistamine combinations are used clinically for their synergistic effect in the management of pain and maintenance of dissociative anesthesia (sedation) in such preparations as Meprozine (meperidine/promethazine) and Diconal (dipipanone/cyclizine), which act as strong anticholinergic agents.
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