Snapshot A 12-year-old boy is brought to the emergency department for difficulty breathing and wheezing. Per the mother, the patient has a history of asthma and has been stable with his rescue inhaler. However, he began coughing 3 days ago and his breathing has gotten progressively worse. A physical examination demonstrates subcostal retractions and diffuse wheezing throughout the lung fields. Overview One of 7 medications used for asthma aimed to reduce inflammation and obstruction Corticosteroids β-agonists Muscarinic antagonists Methylxanthines Cromolyn Antileukotrienes Omalizumab Inhaled Muscarinic Antagonists Mechanism of action competitive blockade of muscarinic receptors which allows for bronchodilation examples tiotropium and ipratropium tiotropium is long-acting Clinical use asthma exacerbation often used in combination with short-acting β-adrenergic agonist chronic obstructive pulmonary disease (COPD) Adverse effects paradoxical bronchospasm angle-closure glaucoma bronchitis