Anticholinergic bronchodilators (or muscarinic receptor antagonists) block the parasympathetic nerve reflexes that cause the airways to constrict, so allow the air passages to remain open. Muscarinic receptor antagonists bind to muscarinic receptors and inhibit acetylcholine mediated bronchospasm.
Anticholinergic bronchodilators are used more to treat chronic obstructive pulmonary disease than to treat asthma.