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Bronchodilators

5 min read

Bronchodilators

Key Points

  • Three major bronchodilator classes: beta-2 agonists (SABAs/LABAs), anticholinergics (SAMAs/LAMAs), and xanthine derivatives (theophylline)
  • SABAs (albuterol): Rescue inhaler for acute bronchospasm — rapid onset 5–15 minutes
  • LABAs (salmeterol): Maintenance therapy — NEVER use as rescue medication; slow onset risks death during acute asthma attack
  • Theophylline: Narrow therapeutic index — requires serum level monitoring every 6–12 months; avoid caffeine
  • All bronchodilators cause tachycardia as a common adverse effect — assess heart rate before and after administration

Drug Class Overview

Bronchodilators are medications that relax and widen the airways to improve airflow in conditions causing bronchoconstriction, including asthma, chronic obstructive pulmonary disease (COPD), and exercise-induced bronchospasm. They act on airway smooth muscle through three distinct receptor mechanisms. Bronchodilators do not treat airway inflammation — they relieve bronchoconstriction only.

Beta-2 Agonists

Mechanism: Stimulate beta-2 adrenergic receptors on bronchial smooth muscle → muscle relaxation → bronchodilation. May also inadvertently stimulate beta-1 receptors → tachycardia.

Short-Acting Beta-2 Agonists (SABAs) — Rescue Inhalers

Agents: Albuterol (Ventolin, Proventil), levalbuterol (Xopenex).

Onset: 5–15 minutes; peak effect 30–60 minutes.

Indications: Acute bronchospasm relief; prevention of exercise-induced bronchospasm (2 inhalations 15 minutes before exercise); acute asthma attacks.

Dosing (Albuterol): 2 inhalations (2.5 mg/inhalation) every 4–6 hours for bronchospasm episodes; some patients need only 1 inhalation every 4 hours.

Key Nursing Points:

  • First-line rescue medication for acute bronchospasm
  • Teach correct inhaler technique: shake, prime before first use, exhale fully before inhaling
  • Rinse mouth with water after use to reduce oral irritation
  • If symptoms worsen or do not improve — seek immediate medical care

Long-Acting Beta-2 Agonists (LABAs) — Maintenance Only

Agents: Salmeterol (Serevent), formoterol.

Onset: Slow (15–30 minutes) — NOT appropriate for acute relief.

Indications: Prevention of bronchospasm in asthma maintenance (always combined with inhaled corticosteroids); COPD management.

Dosing (Salmeterol): 1 inhalation (50 mcg) twice daily, 12 hours apart, in combination with inhaled corticosteroids; for exercise-induced bronchospasm prevention: 1 inhalation 30 minutes before exercise.

LABA Safety — Increased Risk of Asthma-Related Death

LABAs should never be used alone as rescue inhalers and are associated with increased risk of asthma-related death if used as monotherapy during acute attacks due to slow onset. Always combine with inhaled corticosteroids. Never use salmeterol for an active acute bronchospasm.

Adverse Effects (All Beta-2 Agonists): Tremor (most common), tachycardia, palpitations, headache, nervousness, hypokalemia, hyperglycemia, paradoxical bronchoconstriction.

Anticholinergics (Muscarinic Antagonists)

Mechanism: Block acetylcholine at muscarinic receptors on bronchial smooth muscle → inhibit vagally mediated bronchoconstriction → bronchodilation and decreased secretions.

Short-Acting Muscarinic Antagonists (SAMAs)

Agent: Ipratropium bromide (Atrovent).

Indications: COPD (first-line); acute asthma when combined with albuterol (additive bronchodilation).

Dosing: Metered-dose inhaler (17 mcg): 4–8 inhalations with spacer every 20 minutes for 3 doses, then hourly as needed for up to 3 hours. Nebulization (500 mcg): 3–4 times daily, 6–8 hours apart.

Long-Acting Muscarinic Antagonists (LAMAs)

Agent: Tiotropium (Spiriva).

Indications: Long-term maintenance for COPD — reduces exacerbations and improves lung function.

Dosing: 2 inhalations once daily via HandiHaler.

Adverse Effects (Anticholinergics): Dry mouth (most common), headache, dizziness, blurred vision, constipation, urinary retention, tachycardia.

Contraindications: Narrow-angle glaucoma, bladder neck obstruction, prostatic hyperplasia (urinary retention risk).

Xanthine Derivatives

Agent: Theophylline (aminophylline is the IV form).

Mechanism: Inhibits phosphodiesterase enzyme → increased cAMP → bronchial smooth muscle relaxation and suppressed airway responsiveness to bronchoconstrictive stimuli.

Indications: Long-term management of persistent asthma or COPD unresponsive to beta-agonists or inhaled corticosteroids (second/third-line only).

Narrow Therapeutic Index: Requires therapeutic drug level monitoring every 6–12 months; therapeutic serum range: 10–20 mcg/mL; toxicity at >20 mcg/mL.

Key Drug Interactions: Caffeine (additive CNS stimulation, increases toxicity risk) — avoid caffeinated beverages.

Adverse Effects: Nausea, vomiting, CNS stimulation, nervousness, insomnia, tachycardia. Toxicity: seizures, severe cardiac arrhythmias.

Administration Tip: Give in the morning to minimize sleep disruption from CNS stimulation.

Nursing Assessment

Before Administration:

  • Assess respiratory rate, SpO2, breath sounds, and degree of respiratory distress
  • Measure heart rate — bronchodilators cause tachycardia
  • Verify SABA vs LABA prescription — never substitute LABA for acute rescue
  • Confirm inhaler technique and device compatibility (MDI, DPI, nebulizer)
  • Use added caution and monitoring for clients with cardiovascular disease, arrhythmias, hypertension, hyperthyroidism, or diabetes

After Administration:

  • Reassess breath sounds, respiratory rate, and SpO2 within 15–30 minutes
  • Document response to bronchodilator therapy
  • Monitor heart rate for significant tachycardia (>120 bpm)
  • Monitor for palpitations, chest discomfort, blood pressure elevation, and clinically relevant glucose increases in at-risk patients

Patient Education:

  • SABA = “rescue” (use when symptomatic); LABA = “maintenance” (use daily as scheduled)
  • Never skip LABA doses even when feeling well; do not use LABA alone during acute attack
  • For combination therapy: use SABA first, then inhaled corticosteroid (wait 1–2 minutes between)
  • Theophylline: take as prescribed; avoid caffeine; report nausea, vomiting, or heart palpitations
  • Rinse mouth after any inhaler use
  • Report increasing frequency of rescue inhaler use (signal of worsening disease control)

Self-Check

  1. A patient having an acute asthma attack is prescribed salmeterol. Is this the correct medication for acute relief? Why or why not?
  2. What is the most important adverse effect to monitor for after administering albuterol? What is its mechanism?
  3. A patient taking theophylline reports nausea, vomiting, and feeling “shaky.” What do you suspect, and what is the priority nursing action?

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