Bronchodilators (β2-agonists, Anticholinergics, Theophylline)
Start with the big picture
β₂-agonists stimulate airway adenylyl cyclase, increasing cAMP and relaxing bronchial smooth muscle. Short-acting agents are used for rapid relief of acute bronchospasm, while long-acting agents support prophylaxis and should not be used alone in asthma. Anticholinergics block M₃ receptors to reduce vagal tone and can provide add-on bronchodilation. Theophylline increases cAMP through phosphodiesterase inhibition and also affects adenosine signaling, respiratory drive, and diaphragm contractility. Its narrow therapeutic window, interaction potential, and serious toxicity limit its role. The lesson connects these mechanisms and cautions to treatment choices, including when inhaled corticosteroids alone are insufficient and when combined bronchodilators may be useful.
What you'll learn
- Explain how β₂-agonists increase cAMP and relax airway smooth muscle.
- Distinguish short-acting and long-acting β₂-agonists by their clinical roles.
- Describe anticholinergic bronchodilation, add-on uses, and key adverse effects.
- Summarize theophylline’s actions, interactions, toxicity, and limited current role.
- Relate bronchodilator choices to asthma treatment strategies.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
