[1][2] 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.
For example, both cause mydriasis, but parasympatholytics reduce accommodation (cycloplegia), whereas sympathomimetics do not.
Parasympatholytic drugs are sometimes used to treat slow heart rhythms (bradycardias or bradydysrhythmias) caused by myocardial infarctions or other pathologies, 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.