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.
Beta2-agonists (bronchodilators) are a group of drugs prescribed to treat asthma. Short-acting beta-agonists (SABAs) provide quick relief of asthma symptoms. They can also be prescribed to be taken before exercising in order to prevent exercise-induced bronchoconstriction.