19.5 : 抗喘息薬：ムスカリン受容体拮抗薬

Muscarinic receptor antagonists, or antimuscarinic agents, are a class of bronchodilators used for asthma treatment. They inhibit the action of acetylcholine, a neurotransmitter that influences the airways through muscarinic receptors.

These agents compete with acetylcholine for the same binding site on the muscarinic receptor to inhibit acetylcholine's downstream effects and block parasympathetic functions like narrowing the pulmonary airways.

Antimuscarinics such as ipratropium bromide are key agents used in asthma therapy.

They block all the muscarinic receptor subtypes, leading to the relaxation of the smooth airway muscles and reduced mucus secretion.

These agents are typically administered via inhalation route to deliver high doses. This limits the CNS side effects of polar agents, such as ipratropium bromide, which are poorly absorbed into the systemic circulation.

Antimuscarinics are generally safe and well-tolerated for asthma management. They may trigger minor systemic effects, including dry mouth, confusion, blurred vision, urinary retention, and constipation.