Description
A metered-dose inhaler consists of three major components; the canister which is produced in aluminium or stainless steel by means of deep drawing, where the formulation resides; the metering valve, which allows a metered quantity of the formulation to be dispensed with each actuation; and an actuator (or mouthpiece) which allows the patient to operate the device and directs the aerosol into the patient's lungs., The formulation itself is made up of the drug, a liquefied gas propellant and, in many cases, stabilising excipients. The actuator contains the mating discharge nozzle and generally includes a dust cap to prevent contamination.
To use the inhaler the patient presses down on the top of the canister, with their thumb supporting the lower portion of the actuator. Actuation of the device releases a single metered dose of the formulation which contains the medication either dissolved or suspended in the propellant. Breakup of the volatile propellant into droplets, followed by rapid evaporation of these droplets, results in the generation of an aerosol consisting of micrometer-sized medication particles that are then inhaled.
Read more about this topic: Metered-dose Inhaler
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