Inhalation Therapy of Airway Disease: Overview

With inhalation therapy, high drug concentrations are delivered directly to the lungs via nebulizers or metered-dose inhalers (MDI), and systemic side effects are avoided or minimized. The onset of action for inhaled bronchodilators and anti-inflammatory drugs is substantially shorter than that of oral or parenteral formulations. Nebulizers have long been used in animals, but the overall efficiency of dug delivery is low and the equipment is cumbersome and inconvenient for owners. Administration of medications via MDI is now commonplace in the treatment of human asthma and appears to be beneficial in the management of animals as well. Human MDI are designed to provide optimal lung delivery following actuation during a slow, deep inhalation. The addition of spacers enables MDI to be used in young children and small animals. Spacers decrease the amount of drug deposited in the oropharynx (up to 80% of the actuated dose with the MDI alone), reducing systemic drug absorption. Equine delivery devices allow MDI to be used in horses. Clinical use in asthmatic cats, dogs with chronic bronchitis, and horses with RAI is promising but anecdotal; clinical trials are needed to determine the most effective therapies. Drugs available in MDI formulations include β₂ agonists, glucocorticoids, ipratropium bromide, cromolyn sodium, and nedocromil.