Medications by Aerosol

Aerosols of water or saline with no other medication are often referred to as "bland." Bland aerosols may be useful in preventing drying of respiratory tract secretions and optimizing mucociliary clearance (see the section on "Bronchial Hygiene Therapy"). Bland aerosols are typically delivered via nebulizer. Most aerosols contain medications intended for inhalation into the lungs, maximizing the pulmonary effect while minimizing the systemic side effects. Bronchodilators and corticosteroids are the most commonly used aerosols and are shown in Table 75-4 .

Bronchodilators

Bronchodilators are the most frequently used aerosolized medications. The beta-agonist agents bind and activate β₂ -adrenergic receptors stimulating airway smooth muscle relaxation. Several different drugs are available in aerosolized form that are categorized as short-acting agents (e.g., albuterol) and long-acting agents (e.g., salmeterol). The anticholinergic agents antagonize the airway muscarinic receptors, blocking the action of acetylcholine on the parasympathetic nervous system, resulting in relaxation of airway smooth muscles. Ipratropium, a short-acting agent, is the only anticholinergic aerosol currently available in the United States. A long-acting anticholinergic agent, tiotropium, is currently in use in Europe and is awaiting U.S. Federal Drug Administration (FDA) approval.

Anti-inflammatory Aerosols

Anti-inflammatory aerosols are frequently used in the management of obstructive lung diseases, such as asthma and COPD. Several corticosteroid agents are currently available (see Table 75-4 ). Complications, such as osteoporosis, associated with long-term use of systemic corticosteroids are significantly reduced with inhaled corticosteroids. At high doses of inhaled corticosteroids, these complications rarely occur.^[16] The mast cell stabilizing agents (cromolyn and nedocromil) are inhaled anti-inflammatory agents that inhibit activation of and mediator release from inflammatory cells. Mast cell stabilizing aerosols are rarely used in adults and are primarily used in the management of pediatric asthma.

Antimicrobial Agents

Although systemic antimicrobial therapy remains the mainstay of pulmonary infection therapy, a number of aerosolized antimicrobial agents are currently used for specific indications. Aerosolized pentamidine is an alternative regimen for Pneumocystis carinii pneumonia prophylaxis in immunocompromised patients who are intolerant to sulfonamides.^[17] Aerosolized tobramycin decreases bacterial load and improves lung function in patients with cystic fibrosis (CF).^[18] Colistin is an aerosolized antibiotic occasionally used in patients with CF.^[19] Aerosolized amphotericin B is used after lung transplantation for Aspergillus prophylaxis.^[20] Nebulized ribavirin should be considered for children^[21] and immunocompromised patients^[22] with respiratory syncytial virus.

Other Aerosolized Medications

A number of other aerosolized medications are occasionally used. Nebulized racemic epinephrine promotes α- and β-adrenergic receptors. It is often used to treat patients with laryngospasm. Aerosolized recombinant human DNase decreases the viscosity of tracheobronchial secretions by cleaving DNA strands making this potentially useful in the management of cystic fibrosis.^[23] Another mucolytic aerosol, inhaled N-acetylcysteine, decreases the viscosity of pulmonary secretions by disrupting protein disulfide bonds. The use of this drug as a mucolytic

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Bronchodilators and Ventilators

Nebulizers or MDIs can be used to deliver aerosolized bronchodilators to patients during mechanical ventilation. MDI is often the preferred method because use of nebulizers with a ventilator can result in infection, alterations in ventilator performance, and damage to the ventilator circuit.^[26] The dose of drug delivered per puff of MDI is significantly less when administered to patients during mechanical ventilation. Thus, to deliver the same dose of medication the number of puffs must be increased. The delivered dose per puff can vary depending on several factors, including humidification, ventilator settings, ventilator circuit, and ventilator-patient synchrony.^{[27] [28]} Therefore the patient must be observed for appropriate clinical responses such as decreased wheezing and decreased airway resistance.^[29] In general, doses of at least 4 puffs of bronchodilator must be delivered for a therapeutic response.