Bronchodilators relax bronchial smooth muscle and widen the airway. Three drug groups reach that goal by different pathways.

Why the side effects make sense

• Beta₂ receptors are also found in skeletal muscle (→ tremor), the liver (→ glycogenolysis, hyperglycemia), and cell membranes, where beta₂ stimulation drives potassium into cells (→ hypokalemia). At high doses selectivity is lost and beta₁ stimulation causes tachycardia and palpitations.
• Inhaled anticholinergics are quaternary compounds that are poorly absorbed, so effects are mostly local (dry mouth). Systemic anticholinergic effects appear when the drug is swallowed or sprayed into the eyes.
• Methylxanthines have a narrow therapeutic range; the same adenosine and phosphodiesterase effects that open the airway also stimulate the heart and brain.

The inhaled route is preferred because it delivers the drug directly to the airway, works faster, and needs a much smaller dose than oral therapy, which lowers systemic adverse effects.

Disease-specific rules (GINA 2026 and GOLD 2026)

• Asthma: SABA-only treatment is no longer recommended for adults and adolescents. Every client receives ICS-containing treatment; the preferred reliever is as-needed low-dose ICS-formoterol (see Topic 28). A LABA must never be used alone in asthma.
• COPD: short-acting bronchodilators (SABA and/or SAMA) relieve symptoms; LABA + LAMA is the default maintenance therapy for clients with significant symptoms or exacerbations (GOLD groups B and E).
• Acute severe asthma: repeated inhaled SABA during the first hour (pMDI with spacer or nebulizer), ipratropium added for severe attacks, systemic corticosteroid early, and IV magnesium sulfate when the response is poor.
• Anaphylaxis with bronchospasm: IM epinephrine (adrenaline) first; inhaled albuterol is an adjunct only (see Topic 29).

Beta₂ agonists

• Caution in coronary artery disease, dysrhythmias, hypertension, hyperthyroidism, seizure disorders, and diabetes (monitor glucose).
• Nonselective beta-blockers (propranolol, nadolol, timolol eye drops) block the bronchodilator effect and can trigger severe bronchospasm — avoid in asthma. Cardioselective beta-blockers (e.g., metoprolol, bisoprolol) are usually acceptable in COPD with a strong cardiac indication; use caution in asthma.
• Loop and thiazide diuretics and systemic corticosteroids add to hypokalemia; hypokalemia increases the risk of digoxin toxicity.
• MAO inhibitors and tricyclic antidepressants can intensify cardiovascular effects.
• Pregnancy and lactation: inhaled albuterol is the preferred reliever in pregnancy; uncontrolled asthma is a greater risk to the fetus than the medicine. Compatible with breastfeeding.

Muscarinic antagonists

• Caution in narrow-angle glaucoma, prostatic hyperplasia or bladder-neck obstruction; avoid with atropine hypersensitivity.
• Additive effects with other anticholinergic drugs (first-generation antihistamines, tricyclics, oxybutynin).

Theophylline

• Raise theophylline levels (toxicity risk): ciprofloxacin, erythromycin and clarithromycin, cimetidine, fluvoxamine, heart failure, liver disease, older age, fever or viral illness, and quitting smoking.
• Lower levels (loss of effect): smoking tobacco or cannabis, phenytoin, carbamazepine, phenobarbital, rifampin, St John's wort.
• Caffeine adds stimulant effects. Caution with dysrhythmias, seizure disorder, and peptic ulcer disease.

Listed in priority order.

1. Airway and breathing first
   • Assess respiratory rate, work of breathing, ability to speak, breath sounds, SpO₂, and mental status before and after each dose.
   • A silent chest, drowsiness, or a rising PaCO₂ during an asthma attack signals impending respiratory failure — call the rapid response team.
   • Oxygen targets differ: asthma — give oxygen if SpO₂ is below 92% and keep it no higher than about 95% in adults; COPD — titrate to 88–92%.
2. Cardiovascular monitoring
   • Check apical pulse and rhythm before and after beta₂ agonists. Report chest pain, new dysrhythmia, or marked tachycardia (commonly above about 120–130/min in adults, per agency parameters) before the next dose.
3. Laboratory monitoring
   • Potassium 3.5–5.0 mEq/L (3.5–5.0 mmol/L) with repeated or continuous SABA, especially with diuretics or steroids.
   • Glucose in clients with diabetes.
   • Theophylline level: 5–15 mcg/mL (28–83 µmol/L) in current practice (older references give 10–20 mcg/mL). Check a level at the start, after dose changes, with new interacting drugs, a change in smoking, or signs of toxicity.
4. Administration
   • When a bronchodilator and an inhaled corticosteroid are both scheduled, give the bronchodilator first.
   • Between puffs of a quick-relief beta₂ agonist, wait about 15–30 seconds (NAEPP); NAEPP sets no wait between puffs of other medicines. Many product leaflets give their own interval (e.g., albuterol HFA: wait about 1 minute and shake again); follow the leaflet or the prescriber.
   • pMDI with spacer is as effective as a nebulizer for most acute asthma and is preferred in many settings (less infection risk, faster).
   • Nebulizer: client upright, mouthpiece or mask sealed, breathe normally until the mist stops; a mask keeps ipratropium out of the eyes less well than a mouthpiece.
   • IV aminophylline: infusion pump only; give the loading dose slowly (not faster than about 25 mg/min) and use cardiac monitoring.
5. Evaluate response — PEF or FEV₁ before and after treatment; increasing reliever use signals poor control and must be reported.

• Know rescue versus maintenance. Albuterol (or ICS-formoterol in a Track 1 asthma plan) relieves symptoms. LAMA and LABA inhalers are taken every day and do not stop an attack.
• Asthma: needing a SABA more than twice a week means asthma is not controlled — see the provider. Do not use a LABA inhaler without an inhaled corticosteroid.
• Inhaler technique
  • pMDI: follow the numbered steps below; a spacer or holding chamber helps any client.
  • Dry-powder inhaler: do not shake, exhale away from the device, then inhale quickly and forcefully.
  • Soft-mist inhaler: slow, deep breath.
  • Capsule inhalers (e.g., tiotropium capsules): never swallow the capsule — it goes in the device.
  • Check the dose counter; prime and clean the device as the product directs.
• Anticholinergics: keep spray and mist away from the eyes; seek emergency care for eye pain, halos, or sudden blurred vision; report difficulty passing urine; sugar-free gum or sips of water help dry mouth.
• Beta₂ agonists: mild shakiness and a fast heartbeat are common; report chest pain, irregular heartbeat, or severe palpitations. Avoid extra stimulants (high caffeine intake, oral decongestants) unless approved.
• Theophylline: take at the same times daily; do not crush or chew extended-release tablets; limit caffeine; tell the provider before starting or stopping smoking and before any new drug (especially antibiotics); report nausea, vomiting, palpitations, or restlessness — early signs of toxicity.

Metered-dose inhaler steps (NAEPP)

1. Take off the cap and shake the inhaler.
2. Breathe out completely.
3. Hold the inhaler in one of three ways: mouthpiece about 1–2 inches (two finger-widths) in front of an open mouth; attached to a spacer or holding chamber; or between the lips. The in-mouth method is not used for inhaled corticosteroids.
4. Without a spacer, press the canister once just as a slow breath in through the mouth begins. With a spacer or holding chamber, press the canister first, then start the slow breath within 5 seconds.
5. Keep breathing in slowly and as deeply as possible.
6. Hold the breath for a slow count of 10, if able.
7. For a quick-relief beta₂ agonist, wait about 15–30 seconds before the next puff (or as the product leaflet directs, often about 1 minute with a shake between puffs).

• SABA (albuterol/salbutamol) = quick relief; LABA and LAMA = daily maintenance
• Beta₂ agonist adverse effects: tremor, tachycardia, hypokalemia, hyperglycemia
• Asthma: LABA never alone; SABA-only treatment no longer recommended — preferred reliever is as-needed ICS-formoterol
• COPD: LABA + LAMA is the default maintenance therapy
• Anticholinergics: dry mouth, urinary retention, angle-closure glaucoma — caution with glaucoma and prostatic hyperplasia
• Give the bronchodilator before the inhaled corticosteroid
• Nonselective beta-blockers can cause bronchospasm in asthma
• Theophylline 5–15 mcg/mL; toxicity = GI symptoms, tachydysrhythmias, seizures; smoking lowers levels, ciprofloxacin/erythromycin/cimetidine raise them
• Terbutaline: boxed warning against prolonged tocolysis
• Anaphylaxis: IM epinephrine first, bronchodilator second