1 Foundations of Respiratory Pharmacology

Bronchodilators and airway relaxation

Bronchodilators open narrowed airways. Beta₂-agonists relax airway smooth muscle, widening the airways and improving airflow.

Albuterol is a short-acting beta₂-agonist (SABA) used for rapid relief of bronchoconstriction. Long-acting beta₂-agonists (LABAs) provide longer-lasting bronchodilation.

Muscarinic antagonists

Muscarinic antagonists block muscarinic effects that promote airway smooth-muscle constriction. Ipratropium is a short-acting muscarinic antagonist, also called an anticholinergic, and is commonly inhaled. Tiotropium is also a muscarinic-antagonist bronchodilator.

These medicines open narrowed airways through a mechanism distinct from the smooth-muscle relaxation produced by beta₂-agonists.

Inflammation control in asthma

Inhaled corticosteroids (ICS) reduce airway inflammation and are important controller medicines in asthma. They are not instant bronchodilators or the main immediate-relief medicines for sudden bronchospasm. Budesonide is an example of a corticosteroid.

In asthma, a long-acting beta₂-agonist (LABA) should be used with an ICS, not alone as controller therapy. LABAs are bronchodilators, not mucolytics.

Leukotrienes and thick secretions

Leukotriene modifiers reduce the effects of leukotrienes, which contribute to airway inflammation and narrowing. Montelukast blocks leukotriene receptors and is a leukotriene modifier.

Mucolytics reduce or change mucus thickness so secretions can be coughed up and cleared more easily. Acetylcysteine is a mucolytic that may be inhaled by nebulizer to help thin thick secretions, including persistent chest congestion with difficult-to-cough-up mucus.

Routes and selected treatment situations

Many respiratory medicines are delivered by inhaler, and some formulations can be given using a nebulizer. Inhaled bronchodilators and inhaled corticosteroids commonly use an inhaler or nebulizer. Ipratropium is commonly inhaled, and acetylcysteine may be inhaled by nebulizer.

Some corticosteroids and leukotriene modifiers may be taken orally. A clinician may prescribe a short course of an oral corticosteroid for a selected significant asthma or COPD flare, or exacerbation, to reduce airway inflammation. Oral corticosteroids are not the routine quick-relief inhaler.

After using an ICS, a patient may be advised to rinse the mouth and spit to lower the risk of local side effects such as oral thrush and hoarseness.

Medication class review

The medication-to-class matches are:

• Albuterol: beta₂-agonist bronchodilator.

• Tiotropium: muscarinic-antagonist bronchodilator.

• Budesonide: corticosteroid.

• Montelukast: leukotriene modifier.

• Acetylcysteine: mucolytic.

These class distinctions reflect the different actions: bronchodilators open narrowed airways, corticosteroids reduce airway inflammation, leukotriene modifiers block leukotriene effects, and mucolytics thin thick secretions. This material is for learning and not for choosing or changing a personal treatment plan.