This article is an overview of the pharmacology of anticholinergic agents. Although several are used in the management of non-neurologic disorders, fewer are used in the treatment of neurologic disorders. Indications include overactive bladder and neurogenic bladder, sialorrhea of Parkinson disease, and treatment of nerve agent poisoning. Anticholinergic syndrome due to neurotoxicity of drugs with anticholinergic properties is also described, along with its management.
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• A large number of medications have anticholinergic properties.
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• Anticholinergic drugs are used for treating neurologic as well as non-neurologic disorders.
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• Adverse effects of this category of drugs include anticholinergic syndrome.
Historical note and terminology
Anticholinergics are substances that block the neurotransmitter acetylcholine in the central and peripheral nervous systems and are administered to reduce the effects mediated by acetylcholine on acetylcholine receptors in neurons through competitive inhibition. Antimuscarinic agents, a type of anticholinergics, are so called because they block muscarine, a poisonous substance found in the Amanita muscaria, a nonedible mushroom species. Muscarine is a toxic compound that competes with acetylcholine for the same receptors. Antimuscarinic agents are atropine, scopolamine, and ipratropium bromide. Atropine and scopolamine are alkaloids naturally occurring in Atropa belladonna and Datura stramonium plants whereas ipratropium bromide is a derivative of atropine used to treat asthma.
Anticholinergic drugs are used in treating a variety of conditions, such as disorders of gastrointestinal (including nausea and vomiting), genitourinary, and respiratory systems. Atropine, an anticholinergic agent, was used in the past as premedication in anesthesia to reduce upper respiratory secretions. This article focuses on the neurologic applications of anticholinergic drugs, mainly in Parkinson disease, as well as adverse neurologic effects of anticholinergic agents--anticholinergic syndrome.
Historically anticholinergic agents were known more for their toxicity than for their therapeutic effects. Datura stramonium was described as a poison by Homer in The Odyssey. Anticholinergics agents were introduced as the first effective drugs for Parkinson disease by Charcot at the end of 19th century. With the advent of levodopa and other new drugs for Parkinson disease, and because of their adverse effects, the use of anticholinergics declined but continues in several other disorders.
Another use of atropine that is of historical interest now is atropine-induced nonconvulsive coma for treatment of various psychoses and obsessive-compulsive disorder between 1950 and 1975 in the United States and some parts of Europe (13). Although use of atropine was eventually abandoned, initial therapeutic results with atropine coma were favorable, and it seemed to be safer and more effective than insulin coma.