Metered-Dose Inhaler (MDI)

Metered-Dose Inhaler (MDI)

Intended learning outcomes

At the end of the session students will be able to:

  1.  Justify scientific role of metered dose inhalers
  2. Discuss on various components of MDI
  3. Recall types of MDI
  4. Enlist the advantages and disadvantages of MDI
  5. Explain proper usage of MDI
  6. Appraise applications of MDI


       Pressurized metered dose inhalers (MDIs) were first introduced in 1950s.

       MDIs have become the most widely used delivery system for the treatment of lung diseases such as asthma and chronic obstructive pulmonary disease (COPD).

       The MDI is readily recognized by the majority of patients who have ever received treatment for asthma in developed countries and, increasingly so, in developing countries.

        Between 2002 and 2008, 47.5% of inhaled medications sold in Europe were MDIs.


MDI (metered dose inhaler) is a device that used to deliver a specific amount of medication to the lungs.

Metered dose inhalers were first developed in 1955 by Riker Laboratories, Now a subsidiary of 3 M Healthcare.

Metered Dose Inhaler (MDI) has a pressurized container of medication that fits into a mouthpiece

A dose of medication is released into lungs by pushing the container into the mouthpiece.

Metered-dose inhaler

A metered-dose inhaler (MDI) 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 usually self-administered by the patient via inhalation.

Metered dose inhalers (MDI) also provided a versatile, reliable, instantly available, self-contained, portable, low cost medical aerosol delivery system for more than 35 years.

Major components

1. The canister which is produced in aluminium or stainless steel by means of deep drawing, where the formulation resides.

2. The metering valve which allows a metered quantity of the formulation to be dispensed with each actuation.

3. An actuator or mouthpiece which allows the patient to operate the device and directs the aerosol into the patient's lungs.

4. Actuator seat:

It holds metering valve and actuator nozzle.

5. Actuator nozzle:

It helps to spread the component into the mouth.

Cross-sectional diagram of metered dose inhaler (MDI).

Types of MDI.

MDIs (Metered Dose Inhaler) are classified in two categories

1.       Non-pressurized MDIs.

2.       Pressurized MDIs.

1.       Non-pressurized MDI.

Portable, inhalation delivery device containing an aqueous solution, suspension or emulsion, which delivers one dose in one or more actuators.

2.       Pressurized MDI.

An inhalation product containing one or more propellants in a pressurized delivery device.

How do we use a metered dose inhaler?
 General steps for COPD:

1. Remove the cap from the metered dose inhaler.

2. Shake the inhaler for a few seconds.

3. Place our index finger on top of the canister and thumb on the bottom of the mouthpiece.

4. Tilt our head back slightly and breathe out.

5. Hold the inhaler upright about the width of two fingers from our mouth.

6. Press down on the inhaler once as we breathe in as slowly and deeply as we can about 3-5 sec.

7. If possible, hold our breath for at least 10 seconds.

8. If our doctor prescribed more than one puff of COPD medication, wait about 1 minute and repeat steps 2-8.

9. Replace the cap on the metered dose inhaler.

10. Gargle and rinse our mouth with water or mouthwash (usually advised only for steroid-type inhalers).

What is a spacer?

       A spacer is a tube that attaches to a metered dose inhaler (MDI).It holds the medication until you can breathe it in. The spacer ensures that anyone who does not use the device correctly gets the COPD medicine from the MDI to their lungs. For this reason, it also lessens side effects.

How do I use a metered dose inhaler with a spacer?

       Remove the caps from the metered dose inhaler and spacer.

        Insert the inhaler into the open end of the spacer.

       Shake the inhaler for a few seconds.

       Breathe out completely.

       Place the mouthpiece of the spacer between your teeth. Seal your lips tightly around it.

       Press the canister once to dispense the medication into the spacer.

        Breathe in slowly through your mouth for about 3 to 5 seconds. If you hear a hornlike sound, slow down. This means you are breathing too quickly.

       Hold your breath for at least 10 seconds.

        If your doctor prescribed more than one puff of COPD medication, wait about 1 minute and repeat steps 3-8.

       Remove the spacer from the inhaler and replace the caps on the inhaler and spacer.

       Gargle and rinse your mouth with water or mouthwash

Types of MDI with brand names

Inhaled Corticosteroids: Control respiratory disease by suppressing overactive immune response in the lungs which can cause inflammation. Various brand names  are available such as Flovent, Azmacort, Beclovent, Vanceril, Budesonide, Qvar and Aerobid.

Inhaled Bronchodilators: Relax the smooth muscles of the lung airways preventing spasms that restrict or cut off the air supply. There are two types of bronchodilators available: long acting and short acting. They are available in different brand names as Ventolin, Proventil, Maxair, Xopenex, Alupent and ProAir.

→Combination Inhalers: Corticosteroids and long-acting bronchodilators are also available in combinations for ease of use and efficacy. Brand names available for metered dose inhalers combining both a steroid and bronchodilator are Advair and Symbicort.

Advantages of MDIs

       Portability it is small size & convenience to patients.

       Usually, it is inexpensive as compared to Dry Powder Inhaler (DPI) & Nebulizer.

       Quick to use than other device

       Enhance drug delivery

       Multidose delivery capability more  than hundred (100) dose are available

       Electrostatic charges  does not reduce drug delivery to the lungs

       Lower risk of bacterial contamination

        Allows pressurized metered dose inhaler use in patient with acute  illness

       No drug preparation is needed.

Disadvantages of MDIs

       Needs correct actuation and inhalation coordination.

       Need to hold breath after inhalation.

       Oropharyngeal drug deposition.

       Requires Propellant.

       Flammability possibility of new HFA propellants.

Applications of MDIs

       Most commonly used delivery system for treating asthma, chronic obstructive pulmonary disease (COPD) and other respiratory diseases.

       The medication in a metered dose inhaler is most commonly a bronchodilator, corticosteroid or a combination of both for the treatment of asthma and COPD. Other medications less commonly used but also administered by MDI are mast cell stabilizers, such as cromoglicate or nedocromil.

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