Learning Objective

• Advantages and uses of MDI

A metered-dose inhaler (MDI), introduced in 1950s is a device that delivers a specific amount of medication to the lungs, in the form of a short burst of aerosolized medicine that is inhaled by the patient. It is the most commonly used delivery system for medications such as bronchodilator, corticosteroid or a combination of both for treating asthma, chronic obstructive pulmonary disease (COPD) and other respiratory diseases.

1. MDIs are pressurized aerosol containers with a metered-dose valve. The valve is placed in an oral mouth piece or adapter.
2. On activating the valve, an exact dose of the medicament is dispensed from the container and the particle size is maintained in such a way that most of the medicament gets deposited in the lungs.
3. Formulated as solution or suspension.
4. The drug in the formulation may be delivered to the patient in a micronized or solubilized form along with the excipients, propellant and/or solvent.
5. The main advantage of the MDIs is the dispensing of an accurate dose of the medicament without contamination or exposure of the remaining material.

Metered-dose inhalers are shown in Figure 12.14.

Figure 12.14 Metered-dose Inhalers