2 Bronchodilators

Bronchodilator roles

Bronchodilators relax airway smooth muscle to relieve or prevent bronchoconstriction. Their roles differ: some are used for short-acting relief, while others provide prolonged bronchodilation for maintenance treatment.

Short-acting beta agonists

Albuterol is a short-acting beta₂ agonist (SABA) used for rapid relief of bronchoconstriction. By stimulating beta₂ receptors, it relaxes airway smooth muscle. Tremor, nervousness, and a fast heartbeat can occur; tremor and palpitations or tachycardia are recognized beta-agonist adverse effects.

Frequent need for a rescue inhaler or poor relief should prompt assessment of symptom control rather than repeated unsupervised dose increases.

Long-acting beta agonists

Salmeterol is a long-acting beta₂ agonist (LABA) that provides prolonged airway smooth-muscle relaxation for maintenance bronchodilation. LABAs are not primarily for immediate rescue of an asthma attack.

In asthma, a LABA should not be used alone; it is used with an inhaled corticosteroid. Some asthma treatment plans use formoterol in an inhaled corticosteroid combination for both maintenance and symptom relief.

Muscarinic antagonists

Anticholinergic bronchodilators block muscarinic signaling in airway smooth muscle, reducing bronchoconstriction. Ipratropium is a short-acting muscarinic antagonist (SAMA), while tiotropium is a long-acting muscarinic antagonist (LAMA).

Ipratropium can be added to a SABA in severe acute asthma to provide additional bronchodilation and reduce the risk of hospital admission. It does not replace anti-inflammatory asthma treatment.

Tiotropium is used for ongoing COPD treatment, not as a quick-relief rescue medicine. Dry mouth is a common adverse effect of tiotropium; urinary retention and worsening narrow-angle glaucoma are important precautions.

Theophylline and toxicity

Theophylline is an oral methylxanthine bronchodilator with a narrow safety margin. Its clearance varies among patients, and interactions or changes in health can affect blood levels, so monitoring may be needed.

Nausea, vomiting, headache, and insomnia may occur. High levels can cause dangerous arrhythmias or seizures. Persistent vomiting and a rapid, irregular heartbeat can signal a dangerously high level and require prompt medical assessment. Serum concentration and possible contributing factors should be evaluated.

Compare the main classes

The classes differ in duration, role, and safety concerns:

• Albuterol — SABA: short-acting relief of bronchoconstriction; tremor and tachycardia can occur.

• Salmeterol — LABA: long-acting maintenance bronchodilation; in asthma, use with an inhaled corticosteroid.

• Ipratropium — SAMA: short-acting anticholinergic that may be added to a SABA in severe acute asthma.

• Tiotropium — LAMA: long-acting maintenance bronchodilator commonly used for COPD.

• Theophylline — methylxanthine: oral bronchodilator with variable clearance and toxicity risk; blood-level monitoring may be needed.