Aparasympatholytic agent is a substance or activity that reduces the activity of theparasympathetic nervous system.[1][2]
The term parasympatholytic typically refers to the effect of adrug, although somepoisons act to block the parasympathetic nervous system as well. Most drugs with parasympatholytic properties areanticholinergics.
Parasympatholytic agents andsympathomimetic agents have similar effects to each other, although some differences between the two groups can be observed. For example, both causemydriasis, but parasympatholytics reduceaccommodation (cycloplegia),[3] whereas sympathomimetics do not.
Parasympatholytic drugs are sometimes used to treat slow heart rhythms (bradycardias orbradydysrhythmias) caused bymyocardial infarctions or other pathologies,[4] as well as to treat conditions that causebronchioles in the lung to constrict, such asasthma. By blocking the parasympathetic nervous system, parasympatholytic drugs can increase heart rate in patients with bradycardic heart rhythms, and open up airways and reduce mucus production in patients with asthma.
Drugs that stimulate the parasympathetic nervous system are called parasympathomimetics or cholinergics. Drugs that inhibit the parasympathetic system are called parasympatholytics or anticholinergics. Drugs that stimulate the sympathetic nervous system are called sympathomimetics or adrenergics. Drugs that inhibit the sympathetic system are called sympatholytics or antiadrenergics.
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