Guide — Aerosol Therapy & Pharmacology
Bronchodilators
Bronchodilators are the medications a respiratory therapist reaches for most — the drugs that open the airway in asthma and COPD. This guide covers the two families you give every shift, the rescue-versus-maintenance split that governs how they are used, their side effects, and what you watch before and after each dose.
9 min read · Aerosol Therapy & Pharmacology
Written by Apex Respiratory Editorial Team
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Overview
Two families of bronchodilators relax airway smooth muscle, each by a different mechanism. β₂-agonists stimulate β₂ receptors — raising intracellular cAMP — to relax smooth muscle directly. Antimuscarinics block M3 muscarinic receptors to remove the vagal bronchoconstrictor tone that holds the airway tight.
Because they work through separate pathways, the two can be combined for additive bronchodilation. Within each family the agents split further into short-acting drugs for rescue and long-acting drugs for maintenance — the distinction that drives nearly every bedside decision about which inhaler does what.
Key Concepts
Four classes cover the bronchodilators an RT handles — two β₂-agonists and two antimuscarinics, each split into short- and long-acting forms by their role.
| Class | Examples | Role |
|---|---|---|
| SABA | Albuterol, levalbuterol | Rescue for acute bronchospasm — onset within minutes, duration 4–6 h |
| LABA | Salmeterol, formoterol | Maintenance — duration 12 h or more; never used alone in asthma |
| SAMA | Ipratropium | Added to a SABA in acute obstruction |
| LAMA | Tiotropium and others | Once-daily maintenance — a mainstay of COPD |
- SABA = short-acting β₂-agonist. Albuterol and levalbuterol are the rescue drugs for acute bronchospasm — they work within minutes and last 4–6 hours.
- LABA = long-acting β₂-agonist. Salmeterol and formoterol are maintenance agents lasting 12 hours or more, and in asthma they are never used alone — always paired with an inhaled corticosteroid.
- SAMA = short-acting antimuscarinic. Ipratropium is added to a SABA in acute obstruction; the albuterol/ipratropium combination is common in acute COPD and severe asthma.
- LAMA = long-acting antimuscarinic. Tiotropium and others are once-daily maintenance drugs and a mainstay of COPD therapy.
Assessment & Findings
- A good response. Improvement in breath sounds, peak flow, and work of breathing after a treatment confirms the bronchodilator is working — the reassessment that justifies the dose.
- Rising rescue-inhaler use. A patient needing their SABA more and more often signals poor control and a maintenance regimen that is not holding.
- Paradoxical bronchospasm. Worsening wheeze right after a dose — rather than relief — suggests the treatment itself is constricting the airway and must be stopped.
- β₂ side effects. A climbing heart rate and a fine tremor track the systemic effect of repeated β₂-agonist dosing and tell you when to slow down.
RT Priorities / Interventions
Giving the drug is only half the job; the RT owns the assessment around it and the watch for adverse effects.
| Family | Adverse Effects |
|---|---|
| β₂-agonists | Tremor, tachycardia, palpitations, hypokalemia, hyperglycemia |
| Antimuscarinics | Dry mouth, urinary retention; caution in narrow-angle glaucoma (keep the mask spray out of the eyes) |
- Assess before and after. Listen to breath sounds, check peak flow or FEV₁, and gauge work of breathing on each side of the treatment so you can prove the response rather than assume it.
- Watch heart rate and tremor. These are the β₂-agonist effects you see soonest; rising tachycardia or a marked tremor during repeated dosing is a signal to reassess.
- Ensure correct device technique. A bronchodilator only works if it reaches the airway — coordinate the dose, keep an antimuscarinic mask spray out of the eyes, and coach the patient’s inhaler or nebulizer technique.
- Stay alert for paradoxical bronchospasm. If wheeze worsens immediately after a dose, treat it as the drug causing harm, stop the treatment, and escalate.
Common Pitfalls
- A LABA as monotherapy in asthma. Long-acting β₂-agonist monotherapy is associated with worse outcomes in asthma — always pair it with an inhaled corticosteroid.
- Overreliance on a SABA. Heavy, escalating rescue-inhaler use is a marker of poor control, not a solution — it should prompt a look at the maintenance regimen, not just more albuterol.
- Missing paradoxical bronchospasm. Treating post-dose worsening as “needs more” instead of recognizing the drug as the cause delays the right response.
- Not reassessing the response. Giving a treatment without checking breath sounds, peak flow, and work of breathing afterward leaves you blind to whether it actually helped.
Board Exam Pearls
- SABA = rescue, LABA = maintenance — and in asthma the LABA always rides with an ICS.
- A LAMA such as tiotropium is a COPD maintenance mainstay, given once daily.
- β₂-agonist effects are tremor, tachycardia, and hypokalemia — the systemic price of β₂ stimulation.
- Antimuscarinic effects are dry mouth and urinary retention, with caution in narrow-angle glaucoma.
- Never a LABA alone in asthma — if a stem offers it as monotherapy, that is the wrong answer.
FAQ
What is the difference between a SABA and a LABA?
Both are β₂-agonists that relax airway smooth muscle, but they differ in onset and duration. A SABA (short-acting β₂-agonist) such as albuterol or levalbuterol works within minutes and lasts about 4–6 hours, making it the rescue agent for acute bronchospasm. A LABA (long-acting β₂-agonist) such as salmeterol or formoterol lasts 12 hours or more and is used for maintenance, not rescue — and in asthma it is never given alone.
Why is a LABA never used alone in asthma?
LABA monotherapy in asthma is associated with worse outcomes, so a long-acting β₂-agonist must always be paired with an inhaled corticosteroid (ICS). The LABA relaxes smooth muscle but does nothing for the underlying airway inflammation that drives asthma; the ICS treats that inflammation. Used together they control symptoms safely, which is why guidelines specify LABA-plus-ICS rather than a LABA on its own.
What are the side effects of β₂-agonists?
Because β₂ stimulation is not perfectly selective and has systemic effects, β₂-agonists can cause tremor, tachycardia, and palpitations, along with hypokalemia and hyperglycemia. These are dose-related and most noticeable with frequent or high-dose use, so the RT watches heart rate and tremor when giving repeated treatments during an exacerbation.
What is the role of antimuscarinics like ipratropium and tiotropium?
Antimuscarinics block M3 muscarinic receptors to remove vagal bronchoconstrictor tone, relaxing airway smooth muscle by a different mechanism than β₂-agonists. Ipratropium is a short-acting antimuscarinic (SAMA) added to a SABA in acute obstruction, while tiotropium and similar agents are long-acting antimuscarinics (LAMA) given once daily as a mainstay of COPD maintenance. Common side effects are dry mouth and urinary retention, with caution in narrow-angle glaucoma.
Put it to work
Bronchodilators treat the obstruction, but the exacerbation behind it shows up as gas exchange. Run a blood gas through the interpreter to read the hypoxemia and CO₂ retention an obstructive flare drives — the picture your treatment is trying to reverse.
Open the ABG Interpreter →Related Resources
Sources
- Gardenhire DS. Rau's Respiratory Care Pharmacology. 10th ed. Elsevier; 2019.
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021.
- Global Initiative for Asthma. Global Strategy for Asthma Management and Prevention (current annual report). GINA.