What is the primary function of a metered-dose inhaler?

The primary function of a metered-dose inhaler (MDI) is to deliver medication directly to the lungs. This method allows for more effective treatment of respiratory conditions, such as asthma or chronic obstructive pulmonary disease (COPD), by delivering the medication directly to the site of action—namely, the airways and lung tissue. This localized delivery maximizes the therapeutic effects while minimizing systemic side effects that could occur with oral or intravenous routes.

The design of an MDI allows the user to inhale a specific dose of medication in aerosolized form with each puff, ensuring that the drug is effectively aerosolized for optimal lung deposition. This targeted delivery is crucial for medications like bronchodilators and corticosteroids, which are commonly used to relieve symptoms and manage inflammation in the respiratory system.

Other choices, such as controlling blood pressure, administering intravenous fluids, or monitoring lung capacity, are functions associated with different medical devices or interventions and do not apply to the specific purpose of an inhaler. Thus, the correct understanding of an MDI's primary function underscores its role in direct respiratory therapy.