pMDIs

pMDI stands for pressurized metered-dose inhaler, a handheld device used to deliver a specific amount of medication to the lungs in aerosol form. A typical pMDI consists of a pressurized canister containing the drug in a propellant with a metering valve and a mouthpiece. When the actuator is pressed, a measured dose is pushed out and inhaled through the mouth. Modern pMDIs use hydrofluoroalkane (HFA) propellants rather than the older chlorofluorocarbons (CFCs).

Mechanism and deposition: The fixed dose is delivered as a short aerosol; the particle size facilitates deposition in the airways. Adequate inhalation requires coordination between actuation and inhalation; spacers or holding chambers can be used to improve deposition and reduce oropharyngeal deposition.

Administration: Steps include verifying readiness, shaking, priming if new device or not used recently, exhaling, actuating once while continuing slow deep inhalation, holding breath briefly, and exhaling. For corticosteroid pMDIs, mouth rinsing and spacer use are recommended to reduce thrush and throat irritation. Use of a dose counter can help track remaining puffs.

Clinical uses: pMDIs are used for asthma and COPD and other bronchospasm conditions. Common medications include short-acting beta-agonists such as albuterol/salbutamol for relief and inhaled corticosteroids for control; combination pMDIs may pair corticosteroids with long-acting beta-agonists like beclomethasone/formoterol or fluticasone/salmeterol.

Advantages and challenges: They are portable and provide rapid onset of action with precise dosing; however, achieving correct technique can be challenging; inappropriate use reduces drug delivery and increases systemic exposure; propellants have safety and environmental concerns, and priming may be required when devices are new or unused for extended periods.

History and regulation: Replaced CFCs with HFAs in many regions due to environmental concerns; some regulators emphasize use of spacers and patient education to optimize therapeutic benefit.