Principles of nebulizer-delivered drug therapy for asthma

The principles of aerosol drug delivery by compressed-air nebulization are described, and the therapeutic agents administered by this process for management of asthma are reviewed. For therapy of acute and chronic asthma, aerosol inhalation has become the primary method of drug administration. Aerosolized particles with aerodynamic diameters of 1 to 5 microns are most efficiently deposited in the lower respiratory tract. Delivery systems for therapeutic aerosols include compressed-air nebulizers and metered-dose inhalers. Compressed-air nebulizers are less efficient than metered-dose inhalers; therefore, the drug dosages recommended for nebulizer solutions are 3 to 10 times higher than those delivered by a metered-dose inhaler. Because many asthma patients are treated with nebulization drug therapy at home, both patients and pharmacists must understand how to use the equipment correctly. Drugs used in aerosol therapy of acute and chronic asthma include the beta 2-receptor agonists epinephrine, isoproterenol, isoetharine, metaproterenol, terbutaline, and albuterol; cromolyn sodium; and the anticholinergic agents atropine and ipratropium bromide. Terbutaline and albuterol have longer durations of action and greater beta 2-receptor selectivity than metaproterenol, isoetharine, and isoproterenol. Cromolyn is a first-line prophylactic agent for asthma management. Atropine is indicated for maintenance therapy of chronic asthma and in combination with the beta 2-receptor agonists for therapy of acute asthma; ipratropium bromide is a new agent similar to atropine but with substantially fewer adverse effects. Acute and chronic asthma may be managed by aerosol administration of beta 2-receptor agonists, cromolyn, and atropine, alone or in combination. Inhalation is the preferred route of drug delivery because small doses of medication provide maximal therapeutic benefit with minimal adverse effects.