The term parasympatholytic typically refers to the effect of a drug, although some poisons act to block the parasympathetic nervous system as well. Most drugs with parasympatholytic properties are anticholinergics.
Parasympatholytic agents and sympathomimetic agents have similar effects to each other, although some differences between the two groups can be observed. For example, both cause mydriasis, but parasympatholytics reduce accommodation (cycloplegia)[3], whereas sympathomimetics do not.
Parasympatholytic drugs are sometimes used to treat slow heart rhythms (bradycardias or bradydysrhythmias) caused by myocardial infarctions or other pathologies[4], as well as to treat conditions that cause bronchioles in the lung to constrict, such as asthma. 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.
^Wilhelm, Helmut (2011). "Disorders of the pupil". Handbook of Clinical Neurology. Vol. 102. Elsevier. pp. 427–466. doi:10.1016/b978-0-444-52903-9.00022-4. ISBN9780444529039. ISSN0072-9752. PMID21601076. 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.
^Cole, Steven G.; Drobatz, Kenneth J. (2008-01-01), Tilley, Larry P.; Smith, Francis W. K.; Oyama, Mark A.; Sleeper, Meg M. (eds.), "Chapter 18 - Emergency Management and Critical Care", Manual of Canine and Feline Cardiology (Fourth Edition), Saint Louis: W.B. Saunders, pp. 342–355, ISBN978-1-4160-2398-2, retrieved 2025-07-31
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