Metered-dose inhalers are handheld devices that are used to pump medicine into the lungs through the mouth. The medicine is filled in a pressurized canister that fits into a boot-shaped mouthpiece.

Metered-dose inhalers are used for the management and emergency treatment of lung ailments such as asthma or chronic obstructive pulmonary disease (COPD). People suffering from these ailments have narrow or constricted air passages. Metered-dose inhalers can be used in a number of other lung diseases such as infection in the lung tissues or high blood pressure in the lungs. Recently, MDIs have also been used to deliver several different drugs in non-respiratory conditions including diabetes, pain disorders, and some genetic disorders. However, MDIs are used primarily for respiratory illnesses when people experience a shortness of breath or difficulty breathing.

Metered-dose inhalers are effective in routinely relieving trouble breathing. Unlike pills, MDIs have the advantage of a direct delivery into the lungs. Since the medicine does not enter the bloodstream, a direct delivery to the lungs lets the medicine work quickly while lowering the risk of side effects. Furthermore, metered-dose inhalers are portable, reliable, and cost effective.

Proper Use

A metered-dose inhaler should be used correctly in order to ensure that the right amount of medicine reaches the lungs. Read the instructions carefully on the inhalers, and ask your pharmacist or doctor to demonstrate how to use it.

In general, however, to use an MDI properly you simply need to follow these simple steps:

1. Remove the cap from the MDI, and shake it well.
2. Breathe out completely.
3. Point the mouthpiece toward yourself, put it between your teeth, and place your lips firmly on the mouthpiece to prevent any medicine from escaping while you are using the inhaler.
4. Slowly start breathing in, and press down on the canister once.
5. Keep breathing in a slow, full inhalation.
6. Hold your breath for around 10 seconds to allow the medicine to reach the lungs.
7. If your doctor advises, repeat the process with another puff.
8. Recap the inhaler when you have taken all puffs.

Spacer

 

A spacer is a tube added onto an inhaler's mouthpiece. The spacer provides a chamber to hold medicine after it has been pushed out of the canister. Spacers convert the released medicine into a mist. Instead of inhaling all in one breath, they allow you to take another breath or two to completely inhale the medicine. Spacers are helpful for children, the elderly, or people who cannot properly time the spray with the inhalation or cannot hold their breath for long enough. Spacers prevent wastage of medicine as the mist is inhaled more slowly, completely, and uniformly, and less of it stays in the mouth or on the tongue.

 

Propellants

 

All metered-dose inhalers contain a propellant, a liquefied gas within the canister that helps spray the drug from the MDI. Traditional MDIs contain the gas chlorofluorocarbon, commonly known as CFC, as a propellant. This gas has been said to have a damaging affect on the earth's ozone layer, though it has low toxicity in humans. Recently, inhalers containing HFA (hydroflouroalkane) propellant are increasingly replacing CFC-propellant inhalers. The HFA propellant is safe and effective and meets the Food and Drug Administration criteria for an ideal propellant.

 

Management

 

Keep track of the amount of medicine you use. Some inhalers have dose counters on the canister holder to count each time the medicine is pushed out. This facilitates tracking so you can keep within your prescribed dose and know when a canister is running low.

 

It is difficult to determine if the inhaler is empty by simply shaking it; some propellant usually remains in the canister even if the medicine is gone. If your inhaler does not have a dose counter, keep some kind of record of the doses used. Check the package insert to see how many doses the canister contains. Depending on the number of doses you need in one day, you can mark on your calendar when you need to refill your inhaler. For example, if your inhaler has 60 doses and you take 2 doses per day, refill the inhaler after 30 days. If you use infrequent doses, you should note the date when you started to use the inhaler, and then replace it as indicated on the package insert (typically after three to four months) or when you think it is no longer effective in relieving your symptoms. Use a permanent marker to write the start date on your inhaler, and mark it on the calendar.

 

Outlook

 

Metered-dose inhalers are patient-friendly and easy to use. If used properly, they can help to make a difference to your illness and life. Carry your MDI with you all the time; knowing you always have one at hand will help you breathe a little easier.