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

Introduction

       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.

Definition

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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