Respiratory Pharmacology and Aerosol/Medication Delivery
Drug classes
Short-acting beta2 agonists (albuterol, levalbuterol) relax bronchial smooth muscle within minutes; adverse effects include tremor, tachycardia, and hypokalemia. Ipratropium blocks muscarinic receptors and is added in acute severe asthma/COPD. Inhaled corticosteroids are controllers, not rescue drugs. Systemic steroids reduce airway inflammation in exacerbations but take hours. Mucolytics (acetylcysteine) can irritate airways and cause bronchospasm. Surfactant is instilled intratracheally for neonatal RDS.
Aerosol delivery
Optimal MMAD is 1–5 µm; larger particles impact the upper airway, smaller ones are exhaled. pMDI with valved holding chamber improves lung deposition and reduces oropharyngeal deposition. Use a tight mask for children, avoid eyes with anticholinergics, and rinse after ICS. Nebulizer flow 6–8 L/min, fill 3–5 mL, and use mouthpiece when possible.
Worked example
A patient with acute asthma receives albuterol 2.5 mg by nebulizer with ipratropium 0.5 mg. If tremor and heart rate 130 develop, the beta2 agonist effect is likely; reduce frequency, check potassium, and continue ipratropium/steroid as indicated. A spacer with pMDI can replace a nebulizer for mild–moderate exacerbation if the patient can coordinate.
Traps
Do not use ICS as rescue therapy. Do not add ipratropium as a single maintenance bronchodilator in asthma. Do not place a nebulizer mask loosely or allow nebulizer mist to hit the eyes.