An anticholinergic agent is a substance that blocks the neurotransmitter acetylcholine in the central and the peripheral nervous system. It inhibits parasympathetic nerve impulses (responsible for the involuntary movement of smooth muscles present in the gastrointestinal tract, urinary tract, lungs, etc.) by selectively blocking the binding of the neurotransmitter acetylcholine to its receptor in nerve cells.
Anticholinergics are divided into three categories in accordance with their specific targets in the central and/or peripheral nervous system: antimuscarinic agents, ganglionic blockers, and neuromuscular blockers.

The antimuscarinics are used in palliative care for the treatment of smooth muscle spasm (e.g., bladder, intestine), drying secretions (sialorrhea, drooling, noisy respiratory secretions or "death rattle"), inoperable intestinal obstruction, and disease-related pyrexia.
The medications include the naturally-occurring belladonna alkaloids (atropine and hyoscine hydrobromide) and a number of semi-synthetic and synthetic derivatives (e.g., oxybutynin, glycopyrrolate, and hyoscine butylbromide).

Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on September 18, 2016.
Palliative Care Formulary. 4th ed. Twycross and Wilcock (eds). palliativedrugs.com Ltd, United Kingdom, 2011. p. 5.